Exercise 21 Page 245

The percent proportion is a proportion that sets the ratio of a part of a whole equal to the ratio of a percent out of 100. We can represent a is p percent of wwith the given proportion. part/whole=percent/100 ⇔ a/w=p/100We can find what 0.4% of 40 is by thinking about 0.4 as the percent and 40 as the whole. Let's substitute p= 0.4 and w= 40 into the formula and solve for a using the Properties of Equality.

a/w=p/100

SubstituteII

p= 0.4, w= 40

a/40=0.4/100

▼

Solve for a

MultEqn

LHS * 40=RHS* 40

a/40* 40=0.4/100 * 40

FracMultDenomToNumber

a/40* 40 = a

a=0.4/100 * 40

MoveRightFacToNum

a/c* b = a* b/c

a=0.4* 40/100

Multiply

Multiply

a=16/100

CalcQuot

Calculate quotient

a= 0.16

Knowing the value of a, let's look at the completed percent proportion. 0.16/40=0.4/100 We found that 0.16 is 0.4 % of 40.