PSLE
Four girls, Mary, Penelope, Hazel and Emily raised money for a charity. Mary and Penelope raised a total of $151. Together, Penelope, Hazel and Emily raised a total of $299. The total amount of money raised by all 4 girls is 5 times the amount that Penelope raised. How much money did Mary raise?
Amount that Penelope and Mary raised = $151
Amount that Penelope, Hazel and Emily raised = $299

Penelope is the repeated identity.

Penelope + Mary = 151 --- (1)
Penelope + Hazel + Emily = 299 --- (2)

Amount that Penelope raised = 1 u
Amount that 4 girls raised = 5 u

(1) + (2)
(Penelope + Mary) + (Penelope + Hazel + Emily) = 151 + 299
Penelope + 4 girls = 450
1 u + 5 u = 450
6 u = 450

1 u = 450 ÷ 6 = 75

Amount that Mary raised
= 151 - 1 u
= 151 - 75
= $76

Answer(s): $76