Q&A - P5 Math

veraclari

Wow Thanks All for ur help! The model part is really killing me.. really appreciate the MD here which makes everything so clear.. now shd ask my girl to attempt e other MD for e first qn on pears and plums again as we re both clueless nd couldn't draw one that incorporated everything. .

Jamesbond

PapayaDad:
Assume 12B and 12G

So Boys sold 60 tickets ; girls sold 36 tickets
So boys get $300 ; girls get $180
Boys get 120 more ; we need to reduce this to 40 only ie need to reduce 80

If we reduce 1 boy ; we reduce five tickets ; which is reduce $25
But there will be one more girl ; ie 3 more tickets ; which is $15 more.
So the difference is reduce by $40

So we need to reduce 2 boys from our initial assumption.

Answer 10 boy 14 girls

Check
10B = 50 tickets = $250
14G = 42 tickets = $210
Correct, boys collected $40 more.
There are 14 girls.
Total tickets sold is 92

:thankyou: PapayaDad.

Jamesbond

A box contained a number of 20 cent and 50 cent coins in the ratio 3:4. When ten 50 cent coins were taken out and replaced by 20 cent coins, the ratio became 7:5. Find the sum of money in the box at first?

Pl help.

MathIzzzFun

Jamesbond:
A box contained a number of 20 cent and 50 cent coins in the ratio 3:4. When ten 50 cent coins were taken out and replaced by 20 cent coins, the ratio became 7:5. Find the sum of money in the box at first?

Pl help.

possible approaches - cross-multiply/UP, units, MD.

Using units:

10 x $0.50 = 25 x $0.20
--> 10 fifty-cent coins were replaced by 25 twenty-cent coins

At first
number of 50c --> 20 units + 10
number of 20c (= 3/4 number of 50c) --> 15 units + 7.5

In the end,
number of 50c --> 20 units
number of 20c (=7/5 number of 50c) --> 28 units

since 25 twenty-cent coins were added, we have:

15 units + 7.5 + 25 = 28 units
1 unit --> 2.5

Sum of money in the box at first
= sum of money in the box in the end
= 20 x 2.5 x $0.50 + 28 x 2.5 x $0.20
= $39

cheers.

snowball

4/7 of Ming’s mass is equal to 2/5 of Rob’s mass.

If Ming puts on 6 kg and Rob loses 12kg, the two men will have the same mass.
a) Draw a clearly labelled model to solve the problem.
b) What is Rob’s mass?

snowball

In January, Mrs Wong spent 2/5 of her salary on rent and $120 on parking fees.

She spent 1/4 of her remaining salary on food and $480 on shopping.
She saved the remaining $1896.
How much was Mrs Wong’s salary for January ?

MathsOlympiadtrainer

snowball:
In January, Mrs Wong spent 2/5 of her salary on rent and $120 on parking fees.

She spent 1/4 of her remaining salary on food and $480 on shopping.
She saved the remaining $1896.
How much was Mrs Wong's salary for January ?

This is a working backwards qn.
3/4 of her remaining salary-> 480+1896= 2376
4/4 of her remaining salary-> 2376/3 * 4= 3168

3/5 of her salary-> 3168+120 = 3288
5/5 of her salary-> 3288/3 * 5 = 5480

Hope that helps.

veraclari

MathIzzzFun:
Jamesbond:
A box contained a number of 20 cent and 50 cent coins in the ratio 3:4. When ten 50 cent coins were taken out and replaced by 20 cent coins, the ratio became 7:5. Find the sum of money in the box at first?

Pl help.
possible approaches - cross-multiply/UP, lunits, MD.

Using units:

10 x $0.50 = 25 x $0.20
--> 10 fifty-cent coins were replaced by 25 twenty-cent coins

At first
number of 50c --> 20 units + 10
number of 20c (= 3/4 number of 50c) --> 15 units + 7.5

In the end,
number of 50c --> 20 units
number of 20c (=7/5 number of 50c) --> 28 units

since 25 twenty-cent coins were added, we have:

15 units + 7.5 + 25 = 28 units
1 unit --> 2.5

Sum of money in the box at first
= sum of money in the box in the end
= 20 x 2.5 x $0.50 + 28 x 2.5 x $0.20
= $39

cheers.

Hi Mathizzfun, can I ask.. how to get the 20units in the first place?

And why cross multiply? TIA!!!

MathIzzzFun

veraclari:
MathIzzzFun:
[quote=\"Jamesbond\"]A box contained a number of 20 cent and 50 cent coins in the ratio 3:4. When ten 50 cent coins were taken out and replaced by 20 cent coins, the ratio became 7:5. Find the sum of money in the box at first?

Pl help.
possible approaches - cross-multiply/UP, lunits, MD.

Using units:

10 x $0.50 = 25 x $0.20
--> 10 fifty-cent coins were replaced by 25 twenty-cent coins

At first
number of 50c --> 20 units + 10
number of 20c (= 3/4 number of 50c) --> 15 units + 7.5

In the end,
number of 50c --> 20 units
number of 20c (=7/5 number of 50c) --> 28 units

since 25 twenty-cent coins were added, we have:

15 units + 7.5 + 25 = 28 units
1 unit --> 2.5

Sum of money in the box at first
= sum of money in the box in the end
= 20 x 2.5 x $0.50 + 28 x 2.5 x $0.20
= $39

cheers.

Hi Mathizzfun, can I ask.. how to get the 20units in the first place?

MathIzzzFun

snowball:
4/7 of Ming's mass is equal to 2/5 of Rob's mass.

If Ming puts on 6 kg and Rob loses 12kg, the two men will have the same mass.
a) Draw a clearly labelled model to solve the problem.
b) What is Rob's mass?

http://i45.tinypic.com/2nret7p.png\">

cheers.

Q&A - P5 Math

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Q&A - P5 Math