Money and Percents

Total:    25q + 5n = 525          where q = number of quarters, n = number of nickels

Also:    q = 0.1n                  number of quarters = 10% number of nickels    (10% = 0.1)

Replace q in the first equation by 0.1n:      

25*0.1*n + 5n = 525  or

2.5n + 5n = 525 or

7.5n = 525 so

n = 525/7.5  or 

n = 70

There are 70 nickels.

ok it takes four quarters to make a dallor. then all you do is mulitply 5 to 4 which give you 21 quarters then mulitply it by 10 (in 10%) then divide by 5 (for the nickels). you get 4.20

Irving has 10% as many quarters as nickels. If Irving has $5.25 in quarters and nickels, how many nickels does he have?

x = nickels ( 0.05 Cent)

y = quarters(0.25 Cent)

$\small{ \begin{array}{rcll} $ 5.25 &=& $0.25 y + $0.05 x \qquad & | \qquad y = 10 \% \cdot x\\ $ 5.25 &=& $0.25 \cdot ( 10 \% \cdot x ) + $0.05 x \\ $ 5.25 &=& $0.25 \cdot ( \frac{10}{100} \cdot x ) + $0.05 x \\ $ 5.25 &=& \frac{$0.25 \cdot10}{100} x + $0.05 x \\ $ 5.25 &=& $0.025 x + $0.05 x \\ $ 5.25 &=& $0.075 x \\ $0.075 x &=& $ 5.25 \\ x &=& \frac{$5.25}{ $0.075 }\\ x &=& 70 \end{array} }$

He has 70 Nickels and 7 Quarters.

70 * 0.05 + 7 * 0.25 = $5.25