Question

Zaid holds up a bag of coins.

The bag contains only 5p and 20p coins.
The ratio of 5p to 20p coins is 2:1

Zaid says
"If all the 5p coins became 20p coins and all the 20p coins became 5p coins
the total value of the coins in the bag would increase by £6."
Work out how many coins are in the bag.

Answer 1

the number of 5p = 2x

and the number of 20p = x

the total value = y

(2x)*(.05) + (x)*(.20)= y .......eqa1

if all 5p became 20p

20p = 2x

5p = x

(x)*(.05) + (2x)*(.20)= y+6 ..... eqa2

subtract the equations

eq2 - eq 1

======================

0.05x + 0.4x =y+6

-

0.1x + 0.2x = y

======================

0.45x= y+6

-

0.3x =y

= 0.15x = 6

x = 40

so number of 5p = 80 coins

and number of 20p = 40 coins