Q&A - P5 Math

[keinic]

Hi Speedmath & MathIzzzfun, thanks so much for your detailed explanations. MathIzzzfun, the diagram really helps


I need help again for the following:

A glass jar which was 3/4 filled with cereal had a mass of 2.1Kg. When 2/15 of the cereal was eaten, the mass of the glass jar with the remaining cereal was 1.84Kg. Find

a. the mass of the empty glass jar in grams.
b. the mass of the glass jar when it was full of cereal in kilograms.

TIA.

[mummyv]

keinic:

Hi Speedmath & MathIzzzfun, thanks so much for your detailed explanations. MathIzzzfun, the diagram really helps


I need help again for the following:

A glass jar which was 3/4 filled with cereal had a mass of 2.1Kg. When 2/15 of the cereal was eaten, the mass of the glass jar with the remaining cereal was 1.84Kg. Find

a. the mass of the empty glass jar in grams.
b. the mass of the glass jar when it was full of cereal in kilograms.

TIA.

hi first time uploading image, if too small sorry
http://i46.tinypic.com/5jzqlg.jpg\">

[Mychildren]

My answer is different.

The empty glass jar should be 2.1-1.95 = 0.15 kg (150g).

This is because base on your model empty jar should be 2.1-(0.13x15)= 0.15kg

[Mychildren]

If full cereal then, 0.13x20 = 2.6kg


Together with glass jar = 2.6 + 0.15 = 2.75kg.

Correct me if I’m wrong. As I would like to learn my mistake if there is any.
Thank You.

[happyheart]

mrswongtuition:

http://i40.tinypic.com/6xyups.jpg\">

Thank you, Mrs Wong

[happyheart]

ruohoo97:

happyheart:

One more questions, thank you again in advance whoever can help


Brandon had 30 spelling tests and collected 36 games cards. With every full marks he scored for a spelling test, he received 2 games cards from his teacher. When he did not score full marks, he had to return 1 games card.

a) how many spelling tests did brandon score full marks?
b) if Brandon wanted to receive a total of 51 games cards, how many spelling tests could he afford not to score full marks?

Using Guess and Check:
a) Brandon had 22 tests score full marks.
b). He needs to score 27 tests full mark, that is 3 test not full mark to get 51 cards.

Thanks ruohoo97, possible to illustrate with detailed solution using guess & check?

[happyheart]

tianzhu:

happyheart:

One more questions, thank you again in advance whoever can help


Brandon had 30 spelling tests and collected 36 games cards. With every full marks he scored for a spelling test, he received 2 games cards from his teacher. When he did not score full marks, he had to return 1 games card.

a) how many spelling tests did brandon score full marks?
b) if Brandon wanted to receive a total of 51 games cards, how many spelling tests could he afford not to score full marks?

Hi

You may use “Make a Supposition” or “Assuming Method”

Assuming Brandon scored full marks for all 30 spelling tests.

30*2 ------ 60

For every test which he didn’t score full marks, he lost (2+1) --- 3 games cards.

60 - 36 --- 24
24/3 --- 8

30 - 8 ------ 22 (spelling tests with full marks).

60 – 51 ------ 9

9/3 -----3 (tests w/o full marks)

Best wishes

Thank you Tianzhu. My DS school has not taught supposition but I can try out this method

[tianzhu]

Mychildren:

If full cereal then, 0.13x20 = 2.6kg


Together with glass jar = 2.6 + 0.15 = 2.75kg.

Correct me if I'm wrong. As I would like to learn my mistake if there is any.
Thank You.

Hi

Your answers are correct.

Best wishes

[Mychildren]

keinic:

Hi Speedmath & MathIzzzfun, thanks so much for your detailed explanations. MathIzzzfun, the diagram really helps


I need help again for the following:

A glass jar which was 3/4 filled with cereal had a mass of 2.1Kg. When 2/15 of the cereal was eaten, the mass of the glass jar with the remaining cereal was 1.84Kg. Find

a. the mass of the empty glass jar in grams.
b. the mass of the glass jar when it was full of cereal in kilograms.

TIA.

Actually,
I did without models,
2/15 -> 0.26kg (2/15 of the cereals)
15/15 -> 1.95kg (1 whole is the 3/4 cereal as 2/15 is out of 3/4)

a) 2.1-1.95=0.15kg (empty jar)

3/4 -> 1.95kg
1 whole full is 4/4 -> 1.95 / (3/4) = 2.6kg
b) 2.6kg + 0.15kg = 2.75kg

[tianzhu]

happyheart:

Thank you Tianzhu. My DS school has not taught supposition but I can try out this method

Hi

\"Make a Supposition\" is one of the heuristics in primary school maths syllabus.

It's not too difficult to grasp it, so it's worthwhile for kids to spend some time learning it.

Best wishes