# coins/inequality word problem

• Sep 9th 2010, 11:47 AM
eunabug
coins/inequality word problem
Bridgett has 64 coins in nickels and dimes. What is the minimum number of dimes she should have to have at least $4.55? Set up the inequality and solve. Thanks • Sep 9th 2010, 12:22 PM Soroban Hello, eunabug! Quote: Bridgett has 64 coins in nickels and dimes. What is the minimum number of dimes she should have to have at least$4.55?
Set up the inequality and solve.

Let: .$\displaystyle \begin{bmatrix}n &=& \text{number of nickels} \\ d &=& \text{number of dimes}\end{bmatrix}$

Then: .$\displaystyle n + d \:=\:64 \quad\Rightarrow\quad n \:=\:64-d$ .[1]

The value of the coins is: .$\displaystyle 5n + 10d$ cents
. . which is to be at least 455 cents.

We have: .$\displaystyle 5n + 10d \:\ge \:455$ .[2]

Substitute [1] into [2]: .$\displaystyle 5(64-d) + 10d \:\ge \:455$

. . $\displaystyle 320 - 5d + 10d \:\ge \:455 \quad\Rightarrow\quad 5d \:\ge\:135 \quad\Rightarrow\quad d \:\ge\:27$

Therefore, Bridgett should have at least 27 dimes.