Math Word Problems Demystified - A Self Teaching Guide

EXAMPLE:Find the interest on a loan whose principal (P) is $4800 at a rate
of 5% for 6 years. UseI¼PRT.

SOLUTION:

GOAL: You are being asked to find the interest.

STRATEGY: Use the formulaI¼PRT.

IMPLEMENTATION:

I¼PRT

¼$ 4800  5 % 6

¼$ 4800 ð 0 : 05 Þ 6

¼$ 1440

EVALUATION: You can estimate the answer by rounding $4800 to $5000
and then finding 5% of $5000, which is 0.05$5000¼$250. The interest for
one year is about $250. The interest for 6 years then is 6$250¼$1500.
Since this is close to $1440, the answer is probably correct.

EXAMPLE: Find the Celsius temperature (C) when the Fahrenheit
temperature (F) is 86 8. Use C¼^59 ðF
32 Þ.

SOLUTION:

GOAL: You are being asked to find a Celsius temperature.

STRATEGY: Use the formula C¼

5

9

ðF
 32 Þ.

IMPLEMENTATION:

C¼

5

9

ðF
 32 Þ:

C¼

5

9

ð 86 
 32 Þ

¼

5

9

ð 54 Þ

¼ 308

LESSON 7 Using Formulas 61