Decimal P6 2011 PSLE P2 Q

A fruit stall was selling pear at 70 cents each and apples at 40 cents each. Sally bought some pears and Tom bought some apples. Sally spent $1.10 more than Tom but had 7 less fruits than him.
a) How many pears did Sally buy?
b) How much did Tom spend?



0.40  x  7  =  $2.80

1.10  +  2.80  =  $3.90

0.70  -  0.40  =  $0.30

3.90  ÷  0.30  =  13  pears


a) It was  13  pears.

13  +  7  =  20

20   x  0.40  =  $8


b) It was  $8.

---------------------------------------
Alternative solution
---------------------------

0.70 x 7 = $4.90

4.90 + 1.10  =  $6

0.70  -  0.40  =  0.30

6  ÷  0.30  =  20

20  -  7  =  13 pears


a) It was  13  pears.


20  x  0.40  =  $8


b) It was  $8.

Decimal P6 2010 Pei Hwa CA1 Q18

7 apples cost $4.00.

9 oranges cost $11.00.
James bought a total of 1000 apples and oranges for $999.00.
How many apples and how many oranges did he buy?


7 A  +  9 O  --> 1000  Use 7 A and 9 O for the number of apples and oranges respectively to avoid handling fractions or decimals

4 A  +  11 O  -->  999

28 A  +  36 O  -->  4 x 1000 = 4000

28 A  +  77 O  -->  7 x 999 = 6993

41 O  -->  6993  -  4000  =  2993

9 O  -->  9/41  x  2993  =  657 oranges

7 A  -->  1000  -  657  =  343 apples


He bought 343 apples and 657 oranges.

Decimal PSLE 2010 P1 Q20

20. Find the value of 5 ÷ 8. Express your answer as a decimal.


5/8 x 125/125 = 625/1000
                       = 0.625


    0.625
   ______
8 | 5.000
  - 4 8
 --------
       30
     - 24
    ------
         60
      - 56
       ------
           40
         - 40
          ----
             0
          ----

Decimal PSLE 2010 P1 Q21

21. Find the value of 0.16 x 40.  Answer:　6.4
 
 
0.16  x  40  =  1.6  x  4
                   =   6.4

Decimal PSLE 2010 P1 Q23

23. John and Ken went to a funfair. John spent $25 and Ken spent 80¢ less than John. How much money did they spend at the funfair altogether?


25  -  0.80  =  24.20

24.20  +  25  =  $49.20

Decimal PSLE 2010 P2 Q3

Meijun had some money. She used 1/4 of it on a watch and 1/6 of it on a gift. The watch and the gift cost $133.50 altogether.How much money had she left?


1/4 x 3/3 = 3/12

1/6 x 2/2 = 2/12

3 + 2 = 5

12 - 5 = 7

5 u  -->  133.50

7 u  -->  7/5 x 133.50 =  $186.90


She had $186.90 left.

Decimal PSLE 2010 P2 Q8

8. A jar filled with 40 identical screws weighs 1.4 kg. The same jar when filled with 20 identical nails weighs 500 g. The mass of each screw is twice the mass of each nail. What is the mass of the empty jar?


J + 80 u -- > 1.4


J + 20 u -- > 0.5



60 u --> 1.4 - 0.5 = 0.9


20 u --> 20/60 x 0.9 = 0.3



J  -->  0.5 - 0.3 = 0.2 kg


The mass of the empty jar is 0.2 kg.

Decimal P6 2010 SA2 NY P2 Q7

Decimal P6 2010 SA2 Nanyang P2 Q13

Quiny and Mandy saved $5748.40 altogether. 0.4 of Quiny’s savings was $431.50 more than 0.2 of Mandy’s savings. How much more money than Quiny did Mandy save? [4 marks][Answer given: $477.80]


Quiny's money --> 10 Q
Mandy's money --> 10M
4 Q --> 2 M + $431.50

2 M --> 4 Q - $431.50

10 M --> 20 Q - 5 x 431.50 = 20 Q - $2157.50


10 Q + 10 M --> $5748.40

30 Q --> 5748.40 + 2157.50 = 7509.90

10 Q --> 7509.90/3 = $2635.30

10 M --> 2 x 2635.30 - 2157.50 = $3113.10

10 M - 10 Q --> 3113.10 - 2635.30 = $477.80

It was $477.80.


Model Drawing
------------------

431.50 / 2 = $215..75   0.4 = 4/10 = 2/5

Compare 2 units of Q (total 5 units) with 2 units of M (total 10 units)
Q  [][215.75][][          ][][           ][][            ][][             ]   ] $5748.40
M [][][][][][][][][][]                                                            ]

215.75 x 5 = 1078.75

15 u --> 5748.40 - 431.50 = 4669.65

5 u --> 5/15 x 4669.75 = 1556.55

1078.75 - 1556.55 = $477.80

It was $477.80.

Decimal P6 2010 SA2 Maha Bodhi P2 Q6

Mrs Gopal and Mrs Ari went to the supermarket. Both women decided to spend all their money on either apples or pears and they would not buy the same fruit.
If Mrs Gopal bought only pears, she would have 9 more fruit than Mrs Ari.
If she bought only apples, she would have 41 more fruit than Mrs Ari.
How much more money has Mrs Gopal than Mrs Ari?
 
 
40 : 60 = 2 : 3    Number bought   3 : 2 (inverse)
 
Number
G [          ][          ]
A [   ][   ][    ]<9>
 
2 u --> 3 p + 9
 
6 u --> 9 p + 3 x 9 = 9 p + 27
 
 
Number
G [          ][          ][          ]
A [   ][   ]<----- 41 ------>
 
3 u --> 2 p + 41
 
6 u --> 4 u + 2 x 41 = 4 p + 82
 
9 p + 27 --> 4 p + 82
 
5 p --> 82 - 27 = 55
 
1 p --> 55/5 = 11
 
3 p --> 3 x 11 = 33
 
2 u --> 33 + 9 = 42
 
 
42 x 0.60 = $25.20
 
33 x 0.40 = $13.20
 
25.2 - 13.20 = $12
 
It was $12


Alternatively
---------------

40 : 60 = 2 : 3   Number bought  3 : 2 (inverse)


Number


G [          ][          ]
A [   ][   ][   ]<9>




Number


G [          ][         ][          ]
A [   ][   ]<----- 41 ------>


5 u --> 5 p + 9 + 41 = 5 p + 50


5 u - 5 p --> 50


2 u - 2 p --> 2/5 x 50 = 20        Compare only number of pears bought


20 x 0.60 = $12


It was $12.

Decimal P6 2010 SA2 Maha Bodhi P2 Q12

Talik was given some pocket money for recess. He realised that if he had spent $0.80 on each meal, he would have 8 meals fewer than if he had spent $0.60 per meal. Talik spent $0.60 on 8 meals and spent $0.80 on the remaining meals. How many meals did the money last him? [4 marks][Answer given: 26 meals]


8 x 0.60 = $4.80

$0.80 - 0.60 = $0.20

4.80/0.20 = 24 meals --- $0.80

24 x 0.80 = $19.20

19.20 - 4.80 = $14.40

14.40/0.80 = 18 meals

18 + 8 = 26 meals

It was 26 meals.

Decimal P6

Timothy wants to buy a skateboard.It costs $17.25.Every week he saves $1.20 more than the week before.After saving for a number of weeks,he bought the skateboard. a)What is the least number of weeks he needs to save enough to buy the skateboard? b)How much of his savings did he have left after buying the skateboard?


Wk 1 --> $1.20

Wk 2 --> 1.20 + 1.20 x 2 --> $3.60

Wk 3 --> $3.60 + 1.20 x 3 = $7.20

Wk 4 --> $7.20 + 1.20 x 4 --> $12.00

Wk 5 --> 12.00 + 1.20 x 5 = $18.00 > $17.25

a) The least number of weeks he needs to save enough to buy the skateboard is 5.


18.00 - 17.25 = $0.75

b) He has $0.75 left.

Decimal P6 2009 SA2 P2 MGS Q8

8. 1 bottle of shampoo and 1 bottle of bath foam cost $15.50 altogether. Mrs Yeo bought 3 bottles of shampoo and 5 bottles of bath foam for $59.70. How much did one bottle of bath foam cost?

1 S + 1 F --> $15.50

3 S + 5 F --> $59.70

3 S + 3 F --> 3 x 15.50 = 46.50

2 F à 59.70 – 46.50 = 13.20

1 F -- > 13.20 ÷ 2 = $6.60

One bottle of bath foam cost $6.60.

Decimal P6 2009 SA2 P2 MGS Q11

11. The table below shows the charges incurred when making overseas phone call.

Miss Ong made an overseas phone call which lasted 25 ½ min. How much must she pay for the overseas phone call?

25 ½ - 5 = 20 ½

First 5 min -- > $8.00

Balance 20 ½ min -- > 21 x 0.15 = $3.15

3.15 + 8.00 = $11.15

She must pay $11.15 for the overseas phone call.

Decimal P6 2009 SA2 P2 Rulang Q14

14. Mrs Ang stored 48 kg of rice in Container A and 90 kg of rice in Container B. If 3 kg of rice were stored in Container A and 7.5 kg of rice were stored in Container B daily, how many days later would Container B have twice as much as Container A?

           A             B        Multiply column A by 2,

  x 2  --------------------   so that end result is equal

96      48            90        to end result of A (2).

+ 6    + 3    :    + 7.5

----------------------------

  2       1      :       2

----------------------------

96 + 6 u -- > 90 + 7.5 u

1.5 u -- > 96 – 90 = 6

1 u -- > 1/1.5 x 6 = 4

3 u -- > 3 x 4 = 12 kg

12 ÷ 3 = 4 days

It was 4 days later.