Q&A - P5 Math

[MathIzzzFun]

S-H:

Sorry MathizzzFun, can you help me with the second question:-


2) Moses had a total of 408 blue and green counters at first. He lost 3/5 of his blue counters and bought another 32 counters. Then the number of green counters he had was 1/4 of the number of the blue counters left. How many more blue counters than green counters did Moses have at first?

Thank you.

can you check the question - some info is missing.

cheers.

[S-H]

MathIzzzFun:

S-H:

Sorry MathizzzFun, can you help me with the second question:-


2) Moses had a total of 408 blue and green counters at first. He lost 3/5 of his blue counters and bought another 32 counters. Then the number of green counters he had was 1/4 of the number of the blue counters left. How many more blue counters than green counters did Moses have at first?

Thank you.

can you check the question - some info is missing.

cheers.

So sorry MathIzzFun, I missed out the word \"Green\". The question should be:-

Moses had a total of 408 blue and green counters at first. He lost 3/5 of his blue counters and bought another 32 green counters. Then the number of green counters he had was 1/4 of the number of the blue counters left. How many more blue counters than green counters did Moses have at first?

Thank you.

[MathIzzzFun]

S-H:

MathIzzzFun:

[quote=\"S-H\"]Sorry MathizzzFun, can you help me with the second question:-


2) Moses had a total of 408 blue and green counters at first. He lost 3/5 of his blue counters and bought another 32 counters. Then the number of green counters he had was 1/4 of the number of the blue counters left. How many more blue counters than green counters did Moses have at first?

Thank you.

can you check the question - some info is missing.

cheers.

So sorry MathIzzFun, I missed out the word \"Green\". The question should be:-

Moses had a total of 408 blue and green counters at first. He lost 3/5 of his blue counters and bought another 32 green counters. Then the number of green counters he had was 1/4 of the number of the blue counters left. How many more blue counters than green counters did Moses have at first?

Thank you.[/quote]In the end :
Number of Green counters --> 1 unit + 32
Number of Blue counters
--> 4 units + 4 x 32
= 4 units + 128
= 2 x 2 units + 2 x64
= 2 x ( 2 units + 64) --> 2/5 of Blue counters, at first
--> at first, 1/5 of blue counters = 2 units + 64

At first,
Number of Green counters --> 1 unit
Number of Blue counters --> 5 x (2 units + 64) = 10 units + 320

Total number of counters = 11 units + 320 --> 408
1 unit --> 8 counters

9 x 8 + 320 = 392
There were 392 more blue counters than green counters at first.

cheers.

[Charnic]

Pls help.

A, B and C shared some hairpin in the ratio of 2:5:8. After buying 15 hairpins each, their ratio become 7:13:19. Find the total hairpin they have in the end. Thanks

[MathIzzzFun]

CNS:

Pls help.

A, B and C shared some hairpin in the ratio of 2:5:8. After buying 15 hairpins each, their ratio become 7:13:19. Find the total hairpin they have in the end. Thanks

Each bought same number of hairpins, therefore the difference in the number of hairpins will remain the same.

In the end,
A:B:C --> 7u : 13u : 19u --- (13u-7u = 6u, 19u-13u=6u, 19u-7u= 12u)
Total --> 39u

At first,
A:B:C --> 2:5:8 --> 4u : 10u : 16u --- (10u-4u =6u, 16u-10u = 6u, 16u-4u= 12u)

For each of them,
3u --> 15 --- (7u-4u= 13u-10u =19u-16u = 3u)
1u --> 5

Total number of hairpins in the end --> 39 x 5 = 195

cheers.

[Charnic]

Thanks. Can you let me know how would the child know that to multiply at first ratio by 2 ? Is it by guess and check to ensure that the difference ends up constant ? I am grateful to your assistance …

[MathIzzzFun]

CNS:

Thanks. Can you let me know how would the child know that to multiply at first ratio by 2 ? Is it by guess and check to ensure that the difference ends up constant ? I am grateful to your assistance ..

original ratio --> 2:5:8
5-2=3,
8-5=3

whereas the end ratio --> 7:13:19
13-7=6
19-13=6

so, in order to equalize the difference, we multiply the original ratio by 2

here are other examples:

Seven years ago, the ratio of the Samuel's age to George's age was 2: 1. The ratio of their ages is 5 : 3 this year. What will be the ratio of their ages in seven years time?
- http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=8920

- http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=8940

The ratio of the age of Vince to Paul is 7:12. 8 years later, the ratio of the age of Vince to Paul is 39:64. How old is Vince now?
- http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=68&t=25129&start=2100

Jenny had 3/7 as much money as Kenny. If they spent $252 each, Jenny's money will be only 2/7 of Kenny's. How much money did Kenny have more than Jenny?
- http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=67&t=25121&start=1440



cheers.

[Charnic]

Thanks. I think I am slowly understanding now. Is these methods cover under the visible maths text as well ? My pals doesn't seem to have :scared:

[chloecube]

Rainer had $133 and Joel had $57. after buying a story book each, Rainer had 3 times as much money left as Joel. the story book cost the same. how much did each story book cost?


the capacity of the water tank is 800L. it is 5/8 filled with water, 7/16 of the water is used to water the plant. how much water is left in the tank? express your answer as a decimal correct to 2 decimal places.
I got 150L, so does it means my answer shld be 150.00L? doesn’t make sense leh…

[tianzhu]

chloecube:

Rainer had $133 and Joel had $57. after buying a story book each, Rainer had 3 times as much money left as Joel. the story book cost the same. how much did each story book cost?

Hi

A neat way is to use MD.

Hope this helps.

Best wishes

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