Zarah keeps RM80 in her 'Giant Fund' at the end of the first month and continues saving every month, RM10 more than the previous month.(a) Just after Zarah's RM280 deposit, determine the number of weeks that she has saved the money.

Answer 1

How many times does she have to add 10 to 80 to make it to 280
80 + 20*10 = 280
Looks like 20 months to me

Answer 2

Tn= 280
280=80 ( n-1) (10)
200 = 10n - 10
210 = 10n
21 = n