PSLE Math 2022 Files and Pens - Tough Maths Made Simple

[@ewanakku2269]

thanks for the explanation 😃

[@user-kb8xx9pq1i]

thanks

[@jaketan5172]

Alternate algebra solution:
Let T be the total amount of money, f be the cost of each file and p be the cost of each pen.
(a) What is 3f/T =?
Given 4/7 T = 6p ...[1]
3/7 T = 4p + 3f ...[2]
[2]/[1]: (3/7)/(4/7) = (4p + 3f) / 6p
(3/4) x 6p = 4p + 3f
3f = 9/2 p - 4p = 1/2 p
[1]: T = (7/4) x 6p = 21/2 p
Thus 3f/T = (1/2 p) / (21/2 p) = 1/21
(b) What is the total number of files that can be bought using T, where 1 is free for each 5f?
3f/T = 1/21
T = 63f = (5x12 + 3) f
Thus total number of files is 63 + 12 =75