2010 PSLE Math Solutions

2010 PSLE SOLUTIONS fresh from the oven (7 Oct 2010)

These few questions were texted to our mobiles by our students. The following solutions for all to check if they got them right. Our solutions are correct according to the questions provided by our students based on pure memory (the questions were accurate as we have double-checked with other sources). Hope you have done well!

(Paper 2, Q18)
There are 2 tanks A and B. Tank A is 60 x 10 x 40 cm and Tank B is 50 x 20 x 36 cm. Tank B is 1/3 filled with water. Two similar taps are turned on to fill both tanks at 1.2 litres per minute. How long does it take for the height of water in both tanks to be the same?



Solution:

A base area = 60 x 10 = 600 cm2
B base area = 50 x 20 = 1000 cm2

When water flows in at 1.2 ℓ per minute the height will rise differently for both tanks.

Tank A’s height per minute = 1200/600 = 2 cm / min

Tank B’s height per minute = 1200/1000 = 1.2 cm / min

Let time be m when height of water in both tanks become the same;

2 x m = 1.2 x m + 12 cm (1/3 filled at first)

2m = 1.2m + 12
0.8m = 12
m = 15 mins

(Paper 2, Q5)
Gary and Fadzil were in a race. When Gary finished the race, Fadzil had completed 5/8of the race. Gary’s speed is 75m/min faster than Fadzil’s. If their speeds were not changed throughout the race, what is Fadzil’s speed?
.........G F
Dist...8u 5u
Speed 8u 5u

Speed diff = 3u = 75m/min
1u = 25m/min

So, F speed = 5u = 5 x 25 = 125m/min
(Paper 2, Q11)
There are 320 marbles and they are placed into box A, B, C, D. A has the most number of marbles while D has the least number of marbles. The difference of A and the other boxes are 8,13 and 19. How many marbles are there in box D?
A = A; B = A – 8; C = A – 13; D = A – 19

Total = 4A – 40 = 320
4A = 360
A = 90

D = 90 – 19 = 71

(Paper 2, Q16)
Nurul and Peili have $60 altogether. They went shopping and Nurul spent twice as many as Peili. The amount of money Peili left was $7 more than the amount she spent. In the end, Peili had twice as much money as Nurul.
a) How much money did Peili spent?
b) How much money did Nurul had at first?

Model:<----left-----> <------ spent----->
N -> ........[0.5x+3.5][ x ][ x ]
P -> [<---x +7----> ][ x ]

N = 0.5x + 3.5 + 2x
P = 2x + 7

Total = 4.5 x + 10.5 = 60
4.5 x = 49.50
x = 11

a) P spent = $11

b) N at first = 2.5x + 3.50
= 2.5 x 11 + 3.5
= $31