Q&A - PSLE Math

[EC72]

Please help with this question. Thank you.

[TheSolver]

There were fewer than 50 exercise books left at a school bookshop on Monday.
On Tuesday, 1/7 of the exercise books were sold.
On Wednesday, one book fewer than 4/9 of the remaining exercise books were sold.
On Thursday, 2 books more than 3/7 of the remaining exercise books were sold.
How many exercise books did the bookshop have on Monday?

First, you have to find the lowest common multiple of the two denominators of the fractions, which is 7 and 9. So, the LCM is 21. Now, list out the multiples of 21 below 50, which will give you only 21 and 42. Now, you try both numbers.
21:
21*6/7=18
18*5/9=10
10+1=11
11*4/7=6 2/7
6 2/7-2=4 2/7
So, that means that you can't use 21.

42:
42*6/7=36
36*5/9=20
20+1=21
21*4/7=12
12-2=10

Ans:42

[leo_mums]

There were fewer than 50 exercise books left at a school bookshop on Monday.
On Tuesday, 1/7 of the exercise books were sold.
On Wednesday, one book fewer than 4/9 of the remaining exercise books were sold.
On Thursday, 2 books more than 3/7 of the remaining exercise books were sold.
How many exercise books did the bookshop have on Monday?

First, you have to find the lowest common multiple of the two denominators of the fractions, which is 7 and 9. So, the LCM is 21. Now, list out the multiples of 21 below 50, which will give you only 21 and 42. Now, you try both numbers.
21:
21*6/7=18
18*5/9=10
10+1=11
11*4/7=6 2/7
6 2/7-2=4 2/7
So, that means that you can't use 21.

42:
42*6/7=36
36*5/9=20
20+1=21
21*4/7=12
12-2=10

Ans:42

TheSolver!

[belnanna]

Hi all,

THis question has been asked in the forum before..However, there wasnt a detailed explanation to this question... Would some kind soul please help to solve this ..THanks in advance!

If Kenny gives 18 marbles to Andrew, he will have thrice as many marbles as Andrew. If Andrew gives 12 marbles to kenny, he will have 1/9 of the number of marbles that kenny has. How many marbles does Kenny have at first?

[belnanna]

Hi all,

Not too sure how to solve these 2 questions.. Please help.. THanks so much in advance.

1: Mrs Low bought a total of 20 hens and geese for $126.Each goose cost $2 more than a hen. How much did she pay for each goose if she bought 6 fewer hens than geese?

2: Andrew , Annie and Ravin opened a bank account each in January 2008.Every month, Andrew, Annie and Ravin deposited $20,$30 and $45 into their bank accounts respectively. IF Annie's account was $900 after a few months,
a) How much longer did Andrew take than Annie to top up his savings to $900?
b)How much would Ravin have when Andrew had topped up to $900?

[Ender]

Mr Ali and Mr Raju started driving to town A at the same time.
Mr Raju took 6 hours to reach town a while Mr Ali took 9 hours to reach town A.
After 3 hours, both men were left with the same distance to complete.
Find the ratio of the total distance travelled by Mr Raju to that travelled by Mr Ali to reach town A if the both of them drove at a constant speed.

After 3 hrs, Mr Rahu left 3 hrs to go, i.e he traveled half of his distance. Let the total Distance for Mr Raju be 2R.

After 3 hrs, Ali have traveled 1/3 of his distance, since he still have 6 hours to go.Let total distance for Ali be 3A.

The remaining distance for Mr Raju is 1R and Ali is 2A and they are equal.
1R = 2A

Total distance for Mr Raju = 2R = 4A ...... (Since 1R=2A)
Total distance for Ali = 3A

Distance Raju : Ali -> 4 : 3

[EC72]

Mr Ali and Mr Raju started driving to town A at the same time.
Mr Raju took 6 hours to reach town a while Mr Ali took 9 hours to reach town A.
After 3 hours, both men were left with the same distance to complete.
Find the ratio of the total distance travelled by Mr Raju to that travelled by Mr Ali to reach town A if the both of them drove at a constant speed.

After 3 hrs, Mr Rahu left 3 hrs to go, i.e he traveled half of his distance. Let the total Distance for Mr Raju be 2R.

After 3 hrs, Ali have traveled 1/3 of his distance, since he still have 6 hours to go.Let total distance for Ali be 3A.

The remaining distance for Mr Raju is 1R and Ali is 2A and they are equal.
1R = 2A

Total distance for Mr Raju = 2R = 4A ...... (Since 1R=2A)
Total distance for Ali = 3A

Distance Raju : Ali -> 4 : 3

Ender!

[leo_mums]

There were fewer than 50 exercise books left at a school bookshop on Monday.
On Tuesday, 1/7 of the exercise books were sold.
On Wednesday, one book fewer than 4/9 of the remaining exercise books were sold.
On Thursday, 2 books more than 3/7 of the remaining exercise books were sold.
How many exercise books did the bookshop have on Monday?

First, you have to find the lowest common multiple of the two denominators of the fractions, which is 7 and 9. So, the LCM is 21. Now, list out the multiples of 21 below 50, which will give you only 21 and 42. Now, you try both numbers.
21:
21*6/7=18
18*5/9=10
10+1=11
11*4/7=6 2/7
6 2/7-2=4 2/7
So, that means that you can't use 21.

42:
42*6/7=36
36*5/9=20
20+1=21
21*4/7=12
12-2=10

Ans:42

TheSolver, how is it the LCM for 7 and 9 is 21?

[berryspice]

Hi,

Need help to solve this question.
Thanks in advance.

[Ender]

Hi,

Need help to solve this question.
Thanks in advance.

http://www.kiasuparents.com/kiasu/forum ... 3#p1540853