Question

A girl had 20 coins in nickels and dimes whose sum was $1.40. She spent 65cents , using 8 coins. She now has ? nickels.

Answer 1

$0.75 nickels

Explanation:

$1.40-$0.65=$0.75

$0.75 nickels

Answer 2

9 Nickles

Explanation:

Let n = number of nickles and d = number of dimes

d + n = 20 -----------(1) [ total number of coins 20 ]

Dimes = $0.10

Nickles = $0.05

0.1d + 0.05n = $1.40 ---------- (2) [20 coins worth $1.40]

Since d + n = 20

∴ n = 20 - d

Let's substitute n in equation (2)

0.1d + 0.05(20-d) = 1.40

0.1d + 1 - 0.05d = 1.40

0.1d + 0.05d = 1.40 - 1

0.05d = 0.4

d =
`(0.4)/(0.05)`

d = 8

Now put value of d in equation (1)

n + 8 = 20

n = 20 - 8

n = 12

Let's check 8(0.1) + 12(0.05) = $1.40

Now she spent 65 cents using 8 coins.

The only combination of 8 coins worth $0.65 is

5d + 3n = $0.65

Hence, she used 5 dimes and 3 nickles.

Now she has 12 - 3 = 9 Nickles