## Primary 6 August Problem Sums 9

P6-PSP-Aug-Ex 9

Ans:

1– 28 cm

Square num­bers are 1, 4, 9, 16, 25, 36, 49, 64, 81, etc …

The two pos­si­ble square num­bers that add to 74 are 25 and 49

5 cm × 5 cm = 25 cm²

7 cm × 7 cm = 49 cm²

7 cm × 4 = 28 cm

2–  355 more marbles

Num­ber of boys –>  3 + 5 = 8

Units of mar­bles each girl received –> 1u

Units of mar­bles each boy received –>  1u + 30

Total received by the 8 chil­dren –>  1u × 3 + (1u + 30) × 5 = 8u + 150

8u + 150 mar­bles ->  570 marbles

8u –>  570 — 150 = 420 marbles

1u –>  102.5 marbles

(5u + 150) — 3u = 2u + 150

(102.5 × 2) + 150 = 355 more marbles

3–  \$71.50

7 duri­ans + 10 man­goes –> \$57

[1 durian + 1 mango –>  \$7.50] × 7
–>  7 duri­ans + 7 man­goes –>  \$52.50

There­fore, \$57 — \$52.50 = \$4.50 –>  3 mangoes

1 mango–>  \$4.50/ 3 = \$1.50

1 durian –>  \$7.50 — \$1.50 = \$6

4 duri­ans + 3 man­goes –>  \$6 × 4+ \$1.50 × 3 = \$28.50

\$100 — \$28.50 = \$71.50

4–  15 : 6 : 10

Red   :  Blue                      Blue   :   Pur­ple
5      :     2                             3      : 5

–>  15    :     6                             6      : 10

Red   :   Blue   :   Pur­ple
15   :    6    : 10

5–  56 cm

Height of water level at first –>  5/8 × 64 cm = 40 cm

1600 cm³ ÷ (10 × 10) cm² = 16 cm

16 cm + 40 cm = 56 cm

6–  200 cook­ies

[Con­stant Difference]

At first:

In the end –>        Joanna  :  Sharon
3       : 5

2u –> 100

1u –> 50

8u –>  50 × 8 = 400 cook­ies left

600 — 400 = 200 cook­ies

7–  \$13.50

5 small tow­els + 6 big tow­els –>  \$34.50

6 small tow­els + 5 bog tow­els –>  \$34.50 — \$4 = \$31.50

11 small tow­els + 11 big tow­els –>  \$34.50 + \$31.50 = \$66

1 small towel + 1 big towel –> \$66/ 11 = \$6

5 small tow­els + 5 big tow­els –>  \$6 × 5 = \$30

1 big towel –> \$34.50 — \$30 = \$4.50

\$4.50 × 3 = \$13.50

## Primary 5 CA2 Revision 1

P5-CA2-Ex 1

Ans:

1–  3

2–  1

3–  2

Area of square –>  8 cm × 10 cm = 80 cm²

Base of tri­an­gle –>  14 cm — 8 cm = 6 cm

Area of tri­an­gle –>  1/2 × 6 cm × 10 cm = 30 cm

80 cm + 30 cm = 110 cm²

4–  3

5–  2

1 hour –> 60 min × 60 = 3600 sec

3600/100 = 36 sets of 100 seconds

36 × 10 = 360 lol­lipops

6–  2

11.00 a.m. to 12 p.m. –> \$2

12 p.m. to 2.30 p.m. –>  2.5 hours ≈ 3 hours –> 3 × \$1 = \$3

\$3 + \$2 = \$5

## Maths Classes for 2015

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## Primary 4 CA2 Revision 3

P4-CA2-Ex 3

Ans:

1–  376 women

11u –> 2068

1u –> 188

188 × 2 = 376 women

2–  \$49

Cost of 25 crates of apples –>  \$58 × 25 = \$1450

Cost of 3 crates of oranges —  \$1597 — \$1450 = \$147

\$147 ÷ 3 = \$49

3–  \$17

Cost of 6.5 kg of prawns –>  \$24 × 6.5 kg = \$156

Cost of 2 kg of fish –>  \$190 — \$156 = \$34

\$34 ÷ 2 = \$17

P4-CA2-Ex 2

Ans:

1– 152.35

2–  2  1/4

3–  15 013

4–  22   1/50

5–  See below

## Primary 4 CA2 Revision 1

P4-CA2-Ex 1

Ans:

1–  3

2–  4

3–  3

4– 4

5–  2

29/50 + 7/100
= 58/100 + 7/100 = 65/100 = 0.65

6–  3

7–  1

1/3 ≈ 0.333

0.33 = 0.330

0.330 is smaller than 0.333

## Primary 3 August Review 1

P3-Aug-Review 1

Ans:

1– 3

2–  4

3– 2

4–  3

5–  3

6–  3

The clock shows 6.20 p.m..

15 min­utes before 6.20 p.m. –>  6.05 p.m.

7–  1

Orig­i­nal length of string ->  2 m 27 cm -> 227 cm

227 cm — 78 cm = 149 cm

## Primary 6 Prelims Revision 9

P6-Prelims-Ex 9

Ans:

1– \$45

Julian –> 1u

Fred­er­ick –> 2u

Mar­cus –> 6u

5u –> \$25

1u –> \$5

\$5 × 9u = \$45

2–  16 more tricycles

Assume all are tri­cy­cles –> 56 × 3 = 168 wheels

168 — 148 = 20 wheels extra

Each bicy­cle has 1 lesser wheel than each tricycle.

There­fore, 20 ÷ 1 = 20 bicycles

56 — 20 00= 36 tricycles

36 — 20 = 16 more tri­cy­cles than bicycles

3–  \$44

4–  22.5 km/h faster

Mar­cus’ speed –>  270 /4 = 67.5 km/h

Mar­cus’ new speed –>  270/3 = 90 km/h

90 km/h — 67.5 km/h = 22.5 km/h faster

5–  396 boys

Girls –>  1u × 5 = 5u

Boys –>  (1u + 16) × 3 = 3u + 48

8u + 48 –>  976 pupils

8u –> 928

1u –> 116

116 × 3 + 48 = 396 boys

6–  \$2945

7 hand­bags + 5 watches = 3 hand­bags + 11 watches

7 hand­bags — 3 hand­bags = 11 watches — 5 watches

4 hand­bags = 6 watches

6 watches –>  \$285 × 4 = \$1140

1 watch –>  \$1140 ÷ 6 = \$190

\$285 × 7 + \$190 × 5 = \$2945

7–  300 stick­ers

Maxwell –> 100%

Jeanet­ter –> 120%

20/100 × 120% = 24%

120%  - 24% = 96% left

96% –>  288 stickers

1% — 3 stickers

3 × 100 = 300 stick­ers

8–  153 cm

17 + 13 = 30 cm — 3 pieces

1 piece –>  10 cm

14 × 10 cm + 13 cm = 153 cm

## Primary 6 Prelims Revision 8

P6-Prelims-Ex 8

Ans:

1–  966

Low­est com­mon mul­ti­ple of 2, 3 and 7 –> 42

999 ÷ 42 = 23 R 33

23 × 42 = 966

2–  75%

3–  Thou­sandths

4–  12- 7

5–  28%

6–  \$6000

7–  \$2375

8–  94 marks

Total marks for the 3 tests –>  79 marks × 3 = 237

237 — 69 — 74 = 94 marks