Ex. 6 To determine the height of the Aon Center Building (in
Chicago), you measure the shadow cast by the building and find it to
be 142 feet long. Then you measure the shadow cast by a four-foot
post and find it to be 6 inches long. Estimate the building’s height.
Bldg height = post height
bldg shadow post shadow
x = 48
142
6
x = 1136
Ex. 7 You invested a total of $10,000 at 4.5% and 5.5% simple
interest. During 1 year, the two accounts earned $508.75. How much
did you invest in each account?
Int at 4.5% = Prt = x(0.045)(1)
Amt at 4.5% = x
Amt at 5.5% = 10000 - x
Int at 5.5% = Prt = (10000 – x)(0.055)(1)
x(0.045)(1) + (10000 – x)(0.055)(1) = $508.75
-0.01x = -41.25
x = $4125 at 4.5%
So $5875 at 5.5%
Ex. 8 A store has $30,000 of inventory in single-disc DVD players
and multi-disc DVD players. The profit on a single-disc player is 22%
and the profit on a multi-disc player is 40%. The profit for the entire
stock is 35%. How much was invested in each type of DVD player?
Inv for sd = x
Profit for sd = 0.22x
Inv for md = 30000 - x
Profit for md = 0.4(30000 – x)
0.22x + 0.4(30000 – x) = 0.35(30000)
0.22x + 0.4(30000 – x) = 105000
-0.18x = -1500
x = $8333.33 invested in sd
So $21,666.67 invested in md
Ex. 9 A cylindrical can has a volume of 200 cm3 and a radius of 4 cm.
Find the height of the can.
Vol = πr2h
200 = π(4)2h
h = 3.98 cm
p. 107 62, 63, 66, 68, 72, 73, 76, 79, 80, 81, 87