PSLE
Four girls, Erika, Tina, Jade and Anna raised money for a charity. Erika and Tina raised a total of $170. Together, Tina, Jade and Anna raised a total of $305. The total amount of money raised by all 4 girls is 4 times the amount that Tina raised. How much money did Erika raise?
Amount that Tina and Erika raised = $170
Amount that Tina, Jade and Anna raised = $305

Tina is the repeated identity.

Tina + Erika = 170 --- (1)
Tina + Jade + Anna = 305 --- (2)

Amount that Tina raised = 1 u
Amount that 4 girls raised = 4 u

(1) + (2)
(Tina + Erika) + (Tina + Jade + Anna) = 170 + 305
Tina + 4 girls = 475
1 u + 4 u = 475
5 u = 475

1 u = 475 ÷ 5 = 95

Amount that Erika raised
= 170 - 1 u
= 170 - 95
= $75

Answer(s): $75