Nan Hua Primary School PSLE Math Prelim 2006 (Q47)

At first, Jonathan had 2/3 as many stamps as Kevan. After Jonathan bought another 8 stamps and Kevan lost 5 stamps, Jonathan now has 4/5 as many stamps as Kevan. Find the number of stamps Jonathan had at first.


Solution



(Jonathan) 2 units + 8 ----- 4 parts

2 units ----- 4 parts – 8



1 unit is half of 4 parts - 8

1 unit ----- 2 parts – 4 *


(Kevan) 3 units – 5 ----- 5 parts

3 x (2 parts – 4) – 5 ----- 5 parts *

6 parts – 12 – 5 ----- 5 parts

6 parts – 5 parts ----- 12 + 5

1 part ---- 17

Note(*) – 1 unit --- 2 parts – 4,
therefore, 3 units --- 3 x (2 parts – 4)


Jonathan at first

4 parts – 8

= (4 x 17) – 8

= 68 – 8

= 60

Answer: Jonathan had 60 stamps at first.