Maha Bodhi Sch 2007 PSLE Math Prelim Q43

Using 3/5 of his money, Derek could buy 8 similar pens. If he was given an extra dollar, he could use it together with the rest of his money to buy another 6 such pens. How much money had Derek?

Solution


3 units ----- 8 pens (multiply by 2)
2 units + $1 ----- 6 pens (multiply by 3)

6 units ----- 16 pens
6 units + $3 ----- 18 pens

$3 ----- 18 pens – 16 pens = 2 pens
2 pens ----- $3
1 pen ----- $3 divided by 2 = $1.50

14 pens ----- $1.50 x 14 = $21
Less $1 he was given ----- $21 - $1 = $20

Answer: He had $20.