RGS Primary 2009 PSLE Math Prelim Paper 2 Q11

Mrs Kee baked some cookies and packed all the cookies in 12 small boxes and 5 big boxes. There were equal number of cookies in each small box and equal number of cookies in each big box. Each big box contained 14 more cookies than each small box. 18/29 of the cookies baked were packed in small boxes. How many cookies were there in each small box?

Solution

12 small boxes --> 18/29 of cookies
1 small box --> 18/29 divided by 12
= 3/58 of cookies

5 big boxes --> 11/29 of cookies (29/29 - 18/29)
1 big box --> 11/29 divided by 5
= 11/145 of cookies

There were 14 more cookies in each big box than in each small box
11/145 - 3/58 --> 14 cookies
7/290 --> 14 cookies
1/290 --> 14 divided by 7 = 2

(Small box) 3/58 --> 15/290
15/290 --> 15 x 2 = 30

Answer: 30 cookies

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RGS Primary 2009 PSLE Math Prelim Paper 2 Q10

Some secondary one boys were asked to name their favourite sport. Their choices were represented on the pie chart below.

There was an equal number of boys who liked athletics and swimming. 80 boys chose football as their favourite sport.
a) What fraction of the boys liked swimming?
b) Find the total number of secondary one pupils who took part in the survey.

Solution

100% --> 360 degrees
1% --> 360 degrees divided by 100 = 3.6 degrees
(Rugby) 5% --> 5 x 3.6 degrees = 18 degrees


a)
Athletics --> (90 - 18) degrees = 72 degrees
Athletics --> same number as Swimming
Swimming --> 72 degrees

Fraction of boys who liked swimming
--> 72/360 = 1/5

Answer: 1/5 of the boys


b)
Football --> (100 - 25* - 20** - 15)% = 40%
40% --> 80
10 % --> 80 divided by 4 = 20
100% --> 10 x 20 = 200

*25% --> Athletics + Rugby (90 degress is 25% of 360 degrees)
**20% --> Swimming is 1/5 (20%)

Answer: 200 boys

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RGS Primary 2009 PSLE Math Prelim Paper 2 Q9

Tricia has some pink, red and yellow ribbons. 1/3 of them are pink ribbons. Four fewer than 1/3 of the remainder are red ribbons and the remaining 24 are yellow ribbons. How many pink ribbons does Tricia have?

Solution

4 units --> 24 - 4 = 20
1 unit --> 20 divided by 4 = 5
3 units --> 3 x 5 = 15

Answer: 15 pink ribbons

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RGS Primary 2009 PSLE Math Prelim Paper 2 Q8

In the figure below, O is the centre of the circle where OCD is an equilateral triangle. Given that Angle OAB = 20 degrees and Angle AOD = 127 degrees, find Angle BOC.

Solution

Angle DOC --> 60 degrees (Triangle OCD is equilateral)
Angle AOB --> (180 - 20 - 20) degrees
= 140 degrees (Triangle OAB is isosceles)

Angle BOC --> (360 - 140 - 127 - 60) degrees
= 33 degrees

Answer: 33 degrees

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RGS Primary 2009 PSLE Math Prelim Paper 2 Q7

Last year the total age of Mr Tan and his wife was p years old. His wife is 1 year younger than him. What is his wife's age 2 years from now? Express your answer in terms of p.

Solution

Last year

2 units + 1 --> p
2 units --> p - 1
1 unit --> (p -1)/2


Two years from now
--> (p - 1)/2 + 3
= (p - 1)/2 + 6/2
= (p -5)/2

Answer: [(p - 5)/2] years old

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RGS Primary 2009 PSLE Math Prelim Paper 2 Q6

Alice, Beth and Claire had 600 stamps altogether. After Beth had given 30 stamps to Alice, Beth had twice as many stamps as Claire and Alice had to 20 stamps more than Claire. How many stamps did Claire have?

Solution

4 units --> 600 - 20 = 580
1 unit --> 580 divided by 4 = 145

Answer: 145

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RGS Primary 2009 PSLE Math Prelim Paper 2 Q4

Find the number that is exactly between 4/5 and 1 and 1/3.

Solution

4/5 + 1 and 1/3
= 12/15 + 1 and 5/15
= 2 and 2/15

2 and 2/15 divided
= 1 and 1/15

Answer: 1 and 1/15

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RGS Primary 2009 PSLE Math Prelim Paper 2 Q3

When a number is divided by 8, the quotient is 121 with no remainder. What is the remainder when the same number is divided by 9?

Solution

? divided by 8 --> 121
? --> 121 x 8
? --> 968

968 divided by 9
= 107 R5

Answer: 5

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RGS Primary 2009 PSLE Math Prelim Paper 2 Q2

A dress cost $139.95. During a sale, a 20% discount was given. Calculate the sale price of the dress.

Solution

Discount --> 20%
Cost after discount --> 80%

Sale price after discount
--> (80/100) x $139.95 = $111.96

Answer: $111.96

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RGS Primary 2009 PSLE Math Prelim Paper 2 Q1

Find the value of each of the following expressions when y = 6.
a) 3y - 4
b) y + 2y/3

Solution

a)
3(6) - 4
= 18 - 4
= 14

Answer: 14


b)
(6) + 2(6)/3
= 6 + 4
= 10

Answer: 10

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