How many ten-cent coins has Jackson?

Question

Jackson has a sum of money made up of five-cent coins and ten-cent coins. There are 40 coins altogether and the money has a total value of $3.20. How many ten-cent coins has Jackson?

Answer 1

Hi Young,

 

Let X = the number of 5 cent coins

Let Y = the number of 10 cent coins

 

There are 40 coins altogether so X + Y = 40

The total value is $3.20 so .05X + .1Y = 3.20

If you want to make the math a little easier, you can say that the total value is 320 cents and 5X + 10Y = 320Multiply the first equation by 5--> 5X + 5Y = 200 so that you can subtract it from the second equation and eliminate the X term --> 5Y = 120

Divide both sides by 5 --> Y = 24 so there are 24 dimes

Then there must be 16 nickles

 

Plug these back into the equations to make sure they work.

 

Have fun.

 

Dan