Question

a piggy bank contains $2.25.the piggy bank contains only quarters and dimes.There are twice as many dimes as quarters in the bank.How many dimes are in the bank?

Answer 1

A quarter is one fourth, 1⁄4, or 25%
D=0.10
X(0.10) + Y(0.25) = 2.25
X = 2Y

Now, replace the X in the longer equation with its known Y equivalent.
2Y(0.10) + Y(0.25) = 2.25

Multiply out the brackets
0.2Y + 0.25Y = 2.25

Add the Y values together
0.45Y = 2.25

Divide both sides by 0.45
Y = 5

So, now we can replace the Y in the longer equation
X(0.10) + 5(0.25) = 2.25
and resolve that
X(0.10) + 1.25 = 2.25
X(0.10) = 2.25 - 1.25
X(0.10) = 1.00
X = 10

So, there are ten dimes and five quarters