Decimals
DECIMALS AND TIME
When you see a time which uses decimals you have to stop and think
for a minute. Decimal numbers are based on units of 10. Time is not
based on units of 10.
So
3.1 hours isn’t 3 hours and 10 minutes or 3 hours and 1 minute.
3.1 hours is the same as 3 hours and six minutes.
and
1.5 hours is the same as 1 hour and thirty minutes.
WHY? ………. because 1 hour = 60 minutes
So 0.1 (or one tenth) of an hour
is 60 mins divided into 10 bits.
60  10 is 6
0.1 of an hour is 6 minutes
Hint …….
0.5 hours is half an hour ……. so this is 30 minutes
0.25 hours is a quarter of an hour ……. so this is 15 minutes
0.75 hours is three quarters of an hour ……. so this is 45 minutes
So when we want to work out how long 9.4 hours is …….
We know that 0.1 hour is 6 minutes
So
0.4 hours will be 6 mins x 4
so it is 24 minutes
f lex i p
9.4 hours is 9 hours and 24 minutes.
ac k s
1
Decimals
A
1)
Have a go at these:
How much sun was there in each of these places on Tuesday?
Place
Hours of Sunshine
Llandudno
3.7
Whitby
7.5
Southport
4.2
Blackpool
4.6
Brighton
5.1
Kirkcudbright
4.75
Torquay
7.9
Padstow
7.8
Bangor
6.3
Lerwick
3.4
Berwick
4.25
2)
Sun in Hours and
Minutes
How long did these people take to run 800 metres?
(The same method works for minutes and seconds)
Runner
Time in Minutes
Fiona
3.1
Mick
2.5
Steve
3.2
Hattie
2.9
Des
2.8
Della
2.75
Gemma
2.6
Alan
2.7
Minutes and Seconds
Can you guess what might happen if you had 0.15 minutes?
Clue: 0.1 minutes is 6 seconds
0.2 minutes is 12 seconds
so 0.015 minutes is 9 seconds
3)
1.35
2.45
7.95
7.65
Circle the right answers to these questions.
minutes = 1 min 35 seconds,
1 min 21 secs,
minutes = 2 min 27 seconds,
2 min 30 secs,
minutes = 7 min 95 seconds,
7 min 57 secs,
minutes = 7 min 36 seconds,
7 min 65 secs,
1 min 18 secs
2 min 45 secs
7 min 18 secs
7 min 39 secs
f lex i p
Check your answers, then discuss with your tutor what you need to
work on next.
ac k s
2
Decimals
Answers
Decimals And Time
A
1)
Place
Hours of Sunshine
Sun in Hours and
Minutes
Llandudno
3.7
3 hours 42 mins
Whitby
7.5
7 hours 30 mins
Southport
4.2
4 hours 12 mins
Blackpool
4.6
4 hours 36 mins
Brighton
5.1
5 hours 6 mins
Kirkcudbright
4.75
4 hours 45 mins
Torquay
7.9
7 hours 54 mins
Padstow
7.8
7 hours 48 mins
Bangor
6.3
6 hours 18 mins
Lerwick
3.4
3 hours 24 mins
Berwick
4.25
4 hours 15 mins
2)
Runner
f lex i p
3)
Minutes and Seconds
Fiona
3.1
3 mins and 6 secs
Mick
2.5
2 mins and 30 secs
Steve
3.2
3 mins and 12 secs
Hattie
2.9
2 mins and 54 secs
Des
2.8
2 mins and 48 secs
Della
2.75
2 mins and 45 secs
Gemma
2.6
2 mins and 36 secs
Alan
2.7
2 mins and 42 secs
1.35
2.45
7.95
7.65
ac k s
Time in Minutes
minutes
minutes
minutes
minutes
=
=
=
=
1 min
2 min
7 min
7 min
21 secs
27 secs
57 secs
39 secs
3