T4N5a
286:
List the first ten multiples of 4 and 6. Then write their first three
common multiples and their L.C.M.
The first ten multiples of 4 are
4, 8, 12, 16, 20, 24, 28, 32, 36, 40
.
The first ten multiples of 6 are
6, 12, 18, 24, 30, 36, 42, 48, 54, 60
The first three common multiples of 4 and 6 are
The L.C.M. of 4 and 6 is
12
.
12, 24, 36
.
.
287:
List the first ten multiples of 8 and 10. Then write their first two
common multiples and their L.C.M.
The first ten multiples of 8 are
8, 16, 24, 32, 40, 48, 56, 64, 72, 80
.
The first ten multiples of 10 are
10, 20, 30, 40, 50, 60, 70, 80, 90, 100
.
The first two common multiples of 8 and 10 are 40, 80
.
The L.C.M. of 8 and 10 is
40
.
288:
List the first ten multiples of 7 and 14. Then write their first
three common multiples and their L.C.M.
The first ten multiples of 7 are
7, 14, 21, 28, 35, 42, 49, 56, 63, 70
.
The first ten multiples of 14 are
14, 28, 42, 56, 70, 84, 98, 112, 126, 140
.
The first three common multiples of 7 and 14 are 14, 28, 42
.
The L.C.M. of 7 and 14 is
14
.
289:
List the first ten multiples of 15 and 20. Then write their first
two common multiples and their L.C.M.
The first ten multiples of 15 are
15, 30, 45, 60, 75, 90, 105, 120, 135, 150
.
The first ten multiples of 20 are
20, 40, 60, 80, 100, 120, 140, 160, 180, 200
.
The first two common multiples of 15 and 20 are 60, 120
.
The L.C.M. of 15 and 20 is
60
.
290:
List the first ten multiples of 6 and 8. Then write their first two
common multiples and their L.C.M.
The first ten multiples of 6 are
6, 12, 18, 24, 30, 36, 42, 48, 54, 60
.
The first ten multiples of 8 are
8, 16, 24, 32, 40, 48, 56, 64, 72, 80
.
The first two common multiples of 6 and 8 are 24, 48
.
The L.C.M. of 6 and 8 is
24
.
291:
List the first ten multiples of 3 and 4. Then write their first two
common multiples and their L.C.M.
The first ten multiples of 3 are
3, 6, 9, 12, 15, 18, 21, 24, 27, 30
.
The first ten multiples of 4 are
4, 8, 12, 16, 20, 24, 28, 32, 36, 40
.
The first two common multiples of 3 and 4 are 12, 24
.
The L.C.M. of 3 and 4 is
12
.
292:
List the first ten multiples of 8 and 12. Then write their first
three common multiples and their L.C.M.
The first ten multiples of 8 are
8, 16, 24, 32, 40, 48, 56, 64, 72, 80
.
The first ten multiples of 12 are
12, 24, 36, 48, 60, 72, 84, 96, 108, 120
.
The first three common multiples of 8 and 12 are 24, 48, 72
.
The L.C.M. of 8 and 12 is
24
.
293:
List the first ten multiples of 16 and 24. Then write their first
three common multiples and their L.C.M.
The first ten multiples of 16 are
16, 32, 48, 64, 80, 96, 112, 128, 144, 160
.
The first ten multiples of 24 are
24, 48, 72, 96, 120, 144, 168, 192, 216, 240
.
The first three common multiples of 16 and 24 are 48, 96, 144 .
The L.C.M. of 16 and 24 is
48
.
294:
List the first ten multiples of 9 and 15. Then write their first two
common multiples and their L.C.M.
The first ten multiples of 9 are
9, 18, 27, 36, 45, 54, 63, 72, 81, 90
.
The first ten multiples of 15 are
15, 30, 45, 60, 75, 90, 105, 120, 135, 150
.
The first two common multiples of 9 and 15 are 45, 90
.
The L.C.M. of 9 and 15 is
45
.
295:
List the first ten multiples of 5 and 15. Then write their first
three common multiples and their L.C.M.
The first ten multiples of 5 are
5, 10, 15, 20, 25, 30, 35, 40, 45, 50
.
The first ten multiples of 15 are
15, 30, 45, 60, 75, 90, 105, 120, 135, 150
.
The first three common multiples of 5 and 15 are 15, 30, 45
.
The L.C.M. of 5 and 15 is
15
.
296:
List the first ten multiples of 14 and 35. Then write their first
two common multiples and their L.C.M.
The first ten multiples of 14 are
14, 28, 42, 56, 70, 84, 98, 112, 126, 140
.
The first ten multiples of 35 are
35, 70, 105, 140, 175, 210, 245, 280, 315, 350
.
The first two common multiples of 14 and 35 are 70, 140
.
The L.C.M. of 14 and 35 is
70
.
297:
List the first ten multiples of 20 and 30. Then write their first
three common multiples and their L.C.M.
The first ten multiples of 20 are
20, 40, 60, 80, 100, 120, 140, 160, 180, 200
.
The first ten multiples of 30 are
30, 60, 90, 120, 150, 180, 210, 240, 270, 300
.
The first three common multiples of 20 and 30 are 60, 120, 180 .
The L.C.M. of 20 and 30 is
60
.
298:
List the first ten multiples of 30 and 45. Then write their first
three common multiples and their L.C.M.
The first ten multiples of 30 are
30, 60, 90, 120, 150, 180, 210, 240, 270, 300
.
The first ten multiples of 45 are
45, 90, 135, 180, 225, 270, 315, 360, 405, 450
.
The first three common multiples of 30 and 45 are 90, 180, 270 .
The L.C.M. of 30 and 45 is
90
.
299:
List the first ten multiples of 6 and 15. Then write their first two
common multiples and their L.C.M.
The first ten multiples of 6 are
6, 12, 18, 24, 30, 36, 42, 48, 54, 60
.
The first ten multiples of 15 are
15, 30, 45, 60, 75, 90, 105, 120, 135, 150
.
The first two common multiples of 6 and 15 are 30, 60
.
The L.C.M. of 6 and 15 is
30
.
300:
List the first ten multiples of 12 and 15. Then write their first
two common multiples and their L.C.M.
The first ten multiples of 12 are
12, 24, 36, 48, 60, 72, 84, 96, 108, 120
.
The first ten multiples of 15 are
15, 30, 45, 60, 75, 90, 105, 120, 135, 150
.
The first two common multiples of 12 and 15 are 60, 120
.
The L.C.M. of 12 and 15 is
60
.
301:
List the first ten multiples of 12 and 16. Then write their first
two common multiples and their L.C.M.
The first ten multiples of 12 are
12, 24, 36, 48, 60, 72, 84, 96, 108, 120
.
The first ten multiples of 16 are
16, 32, 48, 64, 80, 96, 112, 128, 144, 160
.
The first two common multiples of 12 and 16 are 48, 96
.
The L.C.M. of 12 and 16 is
48
.
302:
List the first ten multiples of 22 and 33. Then write their first
three common multiples and their L.C.M.
The first ten multiples of 22 are
22, 44, 66, 88, 110, 132, 154, 176, 198, 220
.
The first ten multiples of 33 are
33, 66, 99, 132, 165, 198, 231, 264, 297, 330
.
The first three common multiples of 22 and 33 are 66, 132, 198 .
The L.C.M. of 22 and 33 is
66
.
303:
List the first ten multiples of 30 and 40. Then write their first
two common multiples and their L.C.M.
The first ten multiples of 30 are
30, 60, 90, 120, 150, 180, 210, 240, 270, 300
.
The first ten multiples of 40 are
40, 80, 120, 160, 200, 240, 280, 320, 360, 400
.
The first two common multiples of 30 and 40 are 120, 240
.
The L.C.M. of 30 and 40 is
120
.
304:
List the first ten multiples of 24 and 36. Then write their first
three common multiples and their L.C.M.
The first ten multiples of 24 are
24, 48, 72, 96, 120, 144, 168, 192, 216, 240
.
The first ten multiples of 36 are
36, 72, 108, 144, 180, 216, 252, 288, 324, 360
.
The first three common multiples of 24 and 36 are 72, 144, 216 .
The L.C.M. of 24 and 36 is
72
.
305:
List the first ten multiples of 6 and 10. Then write their first two
common multiples and their L.C.M.
The first ten multiples of 6 are
6, 12, 18, 24, 30, 36, 42, 48, 54, 60
.
The first ten multiples of 10 are
10, 20, 30, 40, 50, 60, 70, 80, 90, 100
.
The first two common multiples of 6 and 10 are 30, 60
.
The L.C.M. of 6 and 10 is
30
.
1020：
Find the L.C.M. of 4 and 7 using the listing method.
(a) The multiples of 4: 4,
8
,
24
,
28
,
32
,
48
,
52
,
56
,…
(b) The multiples of 7: 7,
12
36
14
,
,
42
,
49
,
56
,
84
,
91
,
98
,…
21
63
,
(c) The common multiples of 4 and 7:
(d) The L.C.M. of 4 and 7 is
28
.
,
16
40
,
,
28
70
28
,
,
,
20
44
,
77
56
,
,
35
,
,…
,
1021:
Find the L.C.M. of 9 and 15. Then write their fourth and fifth
common multiples.
The L.C.M. of 9 and 15 is
45
45
.

4
=
180
The fourth common multiple of
9 and 15 is
45

180
5
=
.
225
The fifth common multiple of 9
and 15 is
225
.
1022:
Find the L.C.M. of 20 and 50. Then write their fourth and fifth
common multiples.
The L.C.M. of 20 and 50 is
100
100
.

4
=
400
The fourth common multiple of
20 and 50 is
100

400
5
=
.
500
The fifth common multiple of 20
and 50 is
500
.
1023:
Bubble Foam
Yellow
20
Yellow
15
Yellow
8
Red
16
Red
Yellow
25
80
Red
Yellow
40
Red
Yellow
30
Yellow
5
96
Red
24
Red
72
Red
Yellow
85
64
Red
(a) Colour the bubble foams which are a multiple of 5 in yellow.
(b) Colour the bubble foams which are a multiple of 8 in red.
(c) There are 2 bubble foams with two colours. The numbers on
these bubble foams are
40 and 80
. They are the
( common multiples / L.C.M. ) of 5 and 8.
(d) Using the listing method, we find that the L.C.M. of 5 and 8
is
40
.
1143：
Remote control toy cars
Billy and David are playing remote control toy cars.
My car takes 6 seconds
to go one round.
My car takes 8 seconds
to go one round.
David
Billy
Fill in the blanks.
(a) The first ten times for Billy’ s car to pass the Start are at the
6th,
12th
42th
,
,
18th
48th
,
,
24th
54th
,
30th
and
,
60th
These 10 numbers are the multiples of
6
36th
,
seconds.
.
(b) The first ten times for David’ s car to pass the Start are at
the 8th,
48th
16th
,
80th
,
56th
24th
,
,
64th
32th
,
,
40th
72th
,
and
seconds.
These 10 numbers are the multiples of
8
.
(c) The two times for the two toy cars to pass the Start together
are at the
24th
and
48th
seconds. These two
numbers are the common multiples of
6
and
(d) The first time for them to pass the Start is at the
8
24th
second. This number is the first common multiple of
and
8
. It is called the
L.C.M.
.
.
6
1144：
The seats in the School Hall
The school is going to hold a speech festival. The headmaster is
telling the janitors to arrange the seats in the school hall.
Please put chairs in
the school hall. You
can put either 12 or
15 chairs in a row.
Think and fill in the blanks.
(a) If there are 12 chairs in a row, the seats needed are the
multiples
72
of 12: 12, 24,
36
,
48
,
60
,
,…
(b) If there are 15 chairs in a row, the seats needed are the
multiples
75
,
of 15: 15,
90
30
,
45
,
60
,
,…
(c) The L.C.M. of 12 and 15 is
60
.
(d) The first eight common multiples of 12 and 15 are
120
,
180
,
420
,
480
.
240
,
300
,
360
60
,
(e) If the number of seats in the school hall is fewer than 450
,
and this number must be a common multiple of 12 and 15, the
maximum number of seats to put in the hall is
420