Tag Archives: problem solving

Primary 6 Prelims Revision 6

P6-Prelims-Ex 6

Ans:

1–  $1225

18% = 9/50

90% = 9/10

There­fore,

Bran­don   :   Charles
50        :     10
5          : 1

6u –> $1470

1u –> $245

$245 × 5u = $1225

 

2–  9/10 h

Time taken to fill 1/9 of the tank –>  2/5 ÷ 4 = 1/10 h

1/10 h × 9 = 9/10 h

 

3–  8 pen­tagons

3 × 5 = 15 match­sticks for the 3 extra pentagons

60 — 15 = 45 match­sticks (The num­ber of squares and pen­tagons are now the same)

Num­ber of match­sticks needed to make 1 square and 1 pen­ta­gon -> 4 + 5
= 9

45/9 = 5

5 + 3 = 8 pen­tagons

 

4–  10 hours

55 min = 11/12 h

11/12 h + 3/4 h = 1   2/3 h

5  1/2 h ÷ 11/12 h = 6 sets

6 × 1   2/3 h = 10 hours

 

5–  $40

85% — 55% = 30%

30% –> $12

100% –>  12/30 × 100 = $40

Con­tinue read­ing

Primary 2 Whole Numbers Level 3 Ex 2

P2-Whole Numbers-L3-Ex 2

Ans:

1–  8 mark­ers

 

2–  8 stamps

3–  569 stick­ers

4–  776 stamps

5–  40 pupils

Qn 5

Num­ber of girls –> 30 ÷ 3 = 10

30 + 10 = 40 pupils

 

6–  9 beads

Total num­ber of beads they had –>  76 + 45 = 121

130 — 121 = 9 beads

 

7–  720 stick­ers

Num­ber of stick­ers Tanya has –>  341 + 38 = 379

379 + 341 = 720 stick­ers

 

8–  537 stamps

Primary 6 SA1 Revision 12

P6-SA1-Ex 12

Ans:

1–  175

2–  $43.50

70% of the price –>  $101.50

30% –>  $101.50/70 × 30 = $43.50

 

3–  (3+ 6) kg

Alan’s mass ->  (+ 3) kg

Nicholas’ mass ->  (m + 3) — 2 = (+ 1) kg

Brett’s mass ->  (+ 1) + 1 = (+ 2) kg

(m + 3) + (+ 1) + (+ 2) = (3+ 6) kg

 

4–  195 km

1  1/2 h× 80 km/h = 120 km

45/60 h × 100 km/h = 75 kg

120 km + 75 km = 195 km

 

5–  $6441.60

Earn­ings in Jan­u­ary –>  122/100 × $6000 = $7320

Earn­ings in Feb­ru­ary –>  88/100 × $7320 = $6441.60

 

6–  30 peo­ple

Frac­tion of men  –>  30/100 = 3/10 = 9/30

Frac­tion of men if 10 women alighted –>  45/100 = 9/20

Women –>  30u — 9u = 21u

20u — 9u = 11u

10u –>  10 women

30 u –>  30 people

Con­tinue read­ing

Primary 2 Whole Numbers Level 3 Ex 1

P2-Whole Numbers-L3-Ex 1

Ans:

1–  241 mar­bles

2–  538 stamps

Num­ber of stamps Irene has –>  325 — 112 = 213

325 + 213 = 538 stamps

 

3–  202 mar­bles

4–  40 pupils

5–  30 apples

Num­ber of apples in each bas­ket –>  2 + 3 = 5

5 × 6 = 30 apples

Con­tinue read­ing

Primary 6 April Problem Sums 5

P6-PSP-Apr-Ex 5

Ans:

1–  30 m

Spaces between 100 trees –> 99

Dis­tance between each tree –> 297 m ÷ 99 = 3 m

3 m × 10 spaces = 30 m

 

2–  28 pupils

Num­ber of pupils who passed one or both sub­jects –> 40 — 2 = 38

30 + 36 = 66

66 — 38 = 28 pupils

 

3–  a ->  (18s + 24) kg ,   b ->   16 kg

Mass of chicken –>  3s kg

Mass of puppy –>  (3s + 4) kg

Mass of dog –>  (3+ 3s + 4) kg × 2 = (12+ 8) kg

3s + 3s + 4 + 12s + 8 = (18s + 12) kg                   (a)

18 × 2 + 12 = 48 kg

48 kg ÷ 3 = 16 kg                           (b)

 

4–  $51.30

Total cost of 5 apples and 5 man­goes –>  $3.25 × 5 = $16.25

Cost of 3 apples –>  $17.60 — $16.25 = $1.35

Cost of 1 apple –> $1.35 ÷ 3 = $0.45

Cost of 1 mango –> $3.25 — $0.45 = $2.80

Cost of 2 man­goes and 7 apples –>  $2.80 × 2 + $0.45 × 7 = $8.70

$50 — $8.70 = $51.30

Con­tinue read­ing

Primary 4 March Problem Sums 5

P4-PSP-Mar-Ex 5

Ans:

1–  $96

2–  28 sweets

Qn 2

If 1 add 12 more sweets to Jacque­line, she will have 1 unit.

4u –>  100 + 12 = 112

112 ÷ 4 = 28 sweets

 

3–  a ->  $8250   b ->  $2475

Amount of money Melanie spent in Jan­u­ary –>  $825 × 2 = $1650

$1650 × 5 = $8250          (a)

$825 + $1650 = $2475      (b)

 

4–  5/8 m

5– 1175 stamps

Roger –> 1u

Joshua –> 4u

4u — 1u = 3u

3u –>  705 stamps

1u –>  235 stamps

235 × 5u = 1175 stamps

Con­tinue read­ing

Primary 5 October Problem Sums 5

P5-PSP-Oct-Ex5

Ans:

1–  $6588

2–  2400 cm³

Amount of water at first –>  4/5 × 30 cm × 20 cm × 30 cm = 14 400 cm³

Amount of water in the end –>  2/3 × 30 cm × 20 cm × 30 cm = 12 000 cm³

14 400 cm³ — 12 000 cm³ = 2400 cm³

 

3–  38 mar­bles

Qn 3

2u –>  96 — 60 = 36

Barry –>  36 ÷ 2 = 18 marbles

Joe –>  60 — 18 = 42 marbles

Tom –>  18 × 3 = 54 marbles

Total –> 54 + 42 + 18= 114 marbles

114 ÷ 3 = 38 mar­bles

 

4–  Cup Y —  160 ml    ,   Cup Z —  60 ml

Y   :   Z
8   : 3

8u + 3 = 11u

11u ÷ 2 = 5.5u

8u — 5.5u = 2.5u

2.5u –>  50 ml

1u –>  20 ml

Cup Y –>  20 ml × 8u = 160 ml

Cup Z –>  20 ml × 3 = 60 ml

 

5–  $651.80

Qn 5

2u –>  $1505 — $201.40 = $1303.60

$1303.60 ÷ 2 = $651.80

 

6–  $15.50

Qn 6

 

2u–  $108 — $71 = $37

1u —  $18.50

Megan –> $18.50 × 3 = $55.50

$71 — $55.50 = $15.50

Con­tinue read­ing

Primary 4 July Problem Sums 3

P4-July-PSP-Ex 3

Ans:

1–  $9153

$2178 + $6975 = $9153

 

2–  5  5/12 kg

The total mass of the nails–>  9   11/12 kg —   11/12 kg = 9 kg

Mass of the nails when they are half-filled –>  9 /2 = 4   1/2 kg

4   1/2 kg +  11/12 kg = 5   5/12 kg

 

3–  3456 canned drinks

128 × 27 = 3456 canned drinks

 

4–  56.58 kg

Qn 4

6u –>  169.74 kg

1u –>  28.29 kg

28.29 kg × 2 = 56.58 kg

Con­tinue read­ing

Primary 6 July Problem Sums 6

P6-July-PSP-Ex 6

Ans:

1–  $800

Frac­tion of money spent on food and shoes –>  1/4 + 1/5 = 9/20

20/20 — 9/20 = 11/20

11u –>  $340 + $100 = $440

1u –> $40

20u –>  $40 ×  20 = $800

 

2–  14 cook­ies

Muffins   :   Cookies

At first  ——>           [   5             :         6   ]  × 2

In the end   ——>    [   2             :        1  ]  × 5

[Make the units of muffins at first and in the end the same]

Muffins   :   Cookies

At first  ———>             10          : 12

In the end  ——->           10          : 5

12u –>  24 cookies

1u –>  2 cookies

5u –>  10 cook­ies left

24 — 10 = 14 cook­ies 

 

3–  Joseph spent more by $2000

3/5 of Terry’s money is equal to 1/3 of Joseph’s money.

[Make the numer­a­tor common]

3/5 of Terry’s is equal to  3/9 of Joseph’s.

Terry   :   Joseph
5         : 9

14u –> $7000

1u –> $500

Amount Terry spent –>  $500 × 5 = $2500

Amount Joseph spent –>  $500 × 9 = $4500

$4500 — $2500 = $2000

Con­tinue read­ing

Primary 4 July Problem Sums 2

P4-July-PSP-Ex 2

Ans:

1–  $144

1/2 u –> $36

1u –>  $36 × 2 = $72

$72 × 2 = $144

 

2–  $487.80

3–  6  4/5 kg

4–  2637 more seashells
Qn 4

7u –>  6328 — 623 = 5705

1u –> 815

Jan­ice –>  815 × 7 = 4075 seashells

Car­o­line –>  815 + 623 =1438 seashells

4075 — 1438 =  2637 more seashells

Con­tinue read­ing