Question

Lin has 13 coins in her pocket that equal 40 cents. All the coins are dimes, d, and pennies, p. Which combination of coins does Lin have? Use the table to answer the question.

Answer 1

To answer this question you should begin with the coin that has a higher value. If you start with the dime and then just add the correct number of pennies to total $0.40, you will see that you will need 3 dimes ($0.30) and 10 pennies ($0.10).

I used a guess and check strategy starting with 2 dimes.

Answer 2

The combination of coins are:

3 dimes and 10 pennies.

Explanation:

Let there are d number of dines and p number of pennies.

Now as there are a total of 13 coins this means that:

d+p=13------(1)

and also the total value of the coins is 40 cents.

1 dime=10 cents

Hence, d dime= 10 d cents

Also, 1 penny= 1 cent

Hence p penny= p cents

Hence, we get:

10d+p=40------(2)

On subtracting equation (1) from (2) we get:

9 d=27

on dividing both side by 9 we get:

d=3

On putting the value of d in equation (1) we get:

3+p=13

i.e. p=13-3

i.e. p=10

The combination is:

3 dimes and 10 pennies