Q&A - PSLE Math

[rose michelle]

Chris had some M&M’s chocolates. He gave 3/10 of them to Ben and 2/5 of the remainder to Ken. He had 105 left. How many M&M’s chocolates had chris at first?

[rose michelle]

Chris had some M&M’s chocolates. He gave 3/10 of them to Ben and 2/5 of the remainder to Ken. He had 105 left. How many M&M’s chocolates had chris at first?

[php]

rose michelle:

Chris had some M&M's chocolates. He gave 3/10 of them to Ben and 2/5 of the remainder to Ken. He had 105 left. How many M&M's chocolates had chris at first?

Ben --> 3/10, remaining --> 7/10
Ken --> 2/5 x 7/10 = 7/25, remaining --> 7/10 - 7/25 = 21/50

21 units --> 105
1 unit --> 105/21 = 5
50 units --> 50 x 5 = 250

Ans : 250

[fightingmom]

rose michelle:

Chris had some M&M's chocolates. He gave 3/10 of them to Ben and 2/5 of the remainder to Ken. He had 105 left. How many M&M's chocolates had chris at first?

Hi ,

You can use the Branching method:

Total
/. \\
Ben. Remainder
3/10. 7/10



Remainder
/. \\
Ken. Left
2/5. 3/5


3/5 = 105
3 units = 105
1 unit = 35
5 units = 175 = 7/10

7 units = 175
1 unit = 25
10 units = 250

Ans: 250

(sorry if you can't see well cos i can't align the numbers properly here )

[speedmaths.012624com]

rose michelle:

Chris had some M&M's chocolates. He gave 3/10 of them to Ben and 2/5 of the remainder to Ken. He had 105 left. How many M&M's chocolates had chris at first?

Hi,

Some P6 pupils may find fractions slightly more difficult to handle than whole numbers.

One method to solve this, without having too many fractions in the working, is “The Denominators are Your Friends Method”

The denominators here are 10 and 5.
10 x 5 = 50

Let Chris have 50u of chocolates at first.
(50u stands for 50 units, or 50 boxes for those used to the Model Method.)

http://i50.tinypic.com/359fksl.jpg\">

21u → 105 chocolates (left)
1u → 5 chocolates
50u → 250 chocolates (at first)

Hope this helps.

Cheers


speedmaths.com


PS.
Parents who wish to find out more about this method may wish to look at the “PSLE Maths Workshop for Parents” thread in the Happenings forum.

.

[tianzhu]

jarenchuatw:

Q2 XiaoMing and Mary each had a certain number of comics. Xiao Ming gave away 40% of his comics and another 15% of his remaining comics to Mary. Then Mary gave 2/3 of her comics to Sally. Xaioming found that he had thrice as many comics left as Mary. If Mary had 210 comics at first,
(a) how many comics did Xiao Ming have at first? (Answer: 500)
(b) how many comics did Sally receive from Mary? (Answer : 170)

Hi

Hope this helps.

Best wishes

http://farm9.staticflickr.com/8005/7207450038_e911da4ea0_z.jpg\">

[tianzhu]

Michaelia0816:

Yay! My exam marks was back, 30 for paper 1 and almost got a* by a few marks! Scoring super well in paper 2!

Hi girl

Well done, keep it going.

Best wishes

[Michaelia0816]

Thank! But I need help with a question:

John has 3 boxes of marbles. There are 2 more marbles in Box A than Box B. There are 18 marbles together in Box A and Box C. The total number of marbles in Box B and Box C is 9 more than the number of marbles in Box A. How many marbles does John have in all?

[tianzhu]

Michaelia0816:

Thank! But I need help with a question:

John has 3 boxes of marbles. There are 2 more marbles in Box A than Box B. There are 18 marbles together in Box A and Box C. The total number of marbles in Box B and Box C is 9 more than the number of marbles in Box A. How many marbles does John have in all?

Hi

You may use MD or use letters of the alphabet.

A ------- B + 2

A + C ------- 18

B + C ------- A + 9

B + C ------- (B + 2) + 9

C ------ 11
A ------- 7
B ------- 5

Total -------- 23

Best wishes

[Michaelia0816]

Thank you! Wow, you are fast in replying, I think you would took 20 min at least!