Singapore Primary Math Explained sc-math

2007 PSLE Math paper - additional solutions

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Updated: 5 November, 2007

2007 PSLE Math questions - solutions

Question 2 (revised)

3
7
of the chairs in a hall were arranged into 18 short rows. Half of the chairs were arranged into 7 long rows and the rest stacked up. There were 16 more chairs in each long row than short row.
a) What fraction of the chairs were stacked up?
b) How many chairs were arranged in rows?
(5 marks)

a)
Fraction of chairs in rows →
3
7
+
1
2
=
13
14


Therefore fraction of chairs stacked up is
1
14


b)

7 long rows → 7 short rows + 7 × 16 chairs

6
14
of chairs → 18 short rows
1
14
of chairs → 18 ÷ 6 = 3 short rows

psle 2007 math solution

14 short rows → 112 chairs
each short row → 112 ÷ 14 = 8 chairs

1
14
of chairs → 3 rows = 3 × 8 = 24 chairs
13
14
of chairs → 13 × 24 = 312 chairs

312 chairs were arranged in rows.

Question 4

Peter saved some $1 coins in the months of May and June. His mother gave him $0.50 for each $1 coin saved in the month of May. Including his mother's contribution, Peter saved a total of $195 in May and June. This was 30% more than his usual savings. How much did Peter save in June?
(4 marks)
130% of usual savings → $195
100% of usual savings → $195 ×
100
130
= $150

mother's contribution → $195 − $150 = $45

mother's contribution → 50% of Peter's savings in May
Peter's savings in May → $45 ×
100
50
= $90

total savings in May → $90 + $45 = $135
savings in June → $190 - $135 = $60

Peter saved $60 in June

Question 5

Karen, Lena and May shared some stickers in the ratio of 3:1:4. After May gave 40% of her stickers to Karen and Lena, Karen had 90 more stickers than May and the number of Lena's stickers increased by 70%.
a) What was the percentage increase for Karen?
b) How many stickers did May have at first?
(5 marks)

May : Karen : Lena → 4 : 3 : 1 → 100% : 75% : 25%

psle 2007 math solution

a)

22.5
75
= 30%

Karen's percentage increase is 30%

b)

37.5% → 90 stickers
100% → 90 ×
100
37.5
= 240 stickers

Mary had 240 stickers at first

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