Q&A - PSLE Math

[MathIzzzFun]

Essential:

The average age of 3 men is 21 years old. If they are of different ages and are at least 17 years old, what is the maximum possible age of the oldest person in the group?

Total age --> 21 x 3 = 63
63 - 17 = 46
So, total age of remaining two persons is 46
Max possible age of oldest of the two = 46-18 = 28

cheers.

[whitety]

MathIzzzFun:

whitety:

Hi, need help on 2 qns.


2) Huiling had 160 less marbles than George. George gave 75% of his marbles to Huiling. Huiling then gave 20% of her marbles to George. If Huiling had 192 more marbles than George in the end, how many marbles did Huiling have at first?

Thanks!

At first,
Huiling --> 16u
George --> 16u + 160 --- 75% = 12u + 120

After George gave 75% to Huiling
Huiling --> 28u + 120 -- 20% = 5.6u + 24
George --> 4u + 40

After Huiling gave 20% to George
Huiling --> 22.4u + 96
George --> 9.6u + 64
Huiling had 192 more, so
9.6u + 64 + 192 = 22.4u + 96
4u --> 50

at first, Huiling --> 200

cheers.

Hi MathIzzzFun,

Thank you very much !

[Essential]

Hi need some help… Q1. Among 20 people who are being interviewed , 12 like basketball and 18 like volleyball . All of them like at least one sport. How many people Like both basket ball and volleyball

[Shimmer]

Shimmer:

Hi Tianzhu


Need your help !

Isaac read a book. 1st day he read 2/5 of it unread. 2nd day he read another 24 page of the book . In the end he read was 5/9the pages did not read. If he finish the rest in 4 days. What was the average number he read for the
Rest of the book?

A rectangle tank was empty at first. Tap A was turned at a rate of 6 litres per min. After 2 min, B drain water at 2liters per min. Both tap turned off after 6 min after Zb was turned on. The tank was 28 cm in height and hold56 litres find the height of water level in tank when both tank turn off.


If a director get two designers work together Work will be completed in 6 days. If A work alone it wil completed in 10 days. He hired A to work on it for a few days and remaining B will do it.How many days A must spend so that it is done in 12 1/2 days?

Can someone help on these 3 questions ?

[ozora]

MathIzzzFun:

whitety:

Hi, need help on 2 qns.


2) Huiling had 160 less marbles than George. George gave 75% of his marbles to Huiling. Huiling then gave 20% of her marbles to George. If Huiling had 192 more marbles than George in the end, how many marbles did Huiling have at first?

Thanks!

At first,
Huiling --> 16u
George --> 16u + 160 --- 75% = 12u + 120

After George gave 75% to Huiling
Huiling --> 28u + 120 -- 20% = 5.6u + 24
George --> 4u + 40

After Huiling gave 20% to George
Huiling --> 22.4u + 96
George --> 9.6u + 64
Huiling had 192 more, so
9.6u + 64 + 192 = 22.4u + 96
4u --> 50

at first, Huiling --> 200

cheers.

Sorry may I know how to get 16units for huiling n 12units +120 for75%?

[balu_priya]

Essential:

Hi need some help.... Q1. Among 20 people who are being interviewed , 12 like basketball and 18 like volleyball . All of them like at least one sport. How many people Like both basket ball and volleyball

12+18=30
30-20=10

[speedmaths.012624com]

Shimmer:

Shimmer:

If a director get two designers work together Work will be completed in 6 days. If A work alone it wil completed in 10 days. He hired A to work on it for a few days and remaining B will do it.How many days A must spend so that it is done in 12 1/2 days?

Can someone help on these 3 questions ?

Hi

Q3

One possible solution/method:

A and B take.... 6 days to do 1 job
A takes............10 days to do 1 job

A and B take.... 60 days to do 10 jobs
A takes.............60 days to do 6 jobs

B takes.............60 days to do 4 jobs
(10 - 6 = 4)

B takes.............60 days to do 4 jobs
B takes.............15 days to do 1 job
A takes.............10 days to do 1 job

B takes.............7.5 days to do 0.5 job
A takes.............5 days to do 0.5 job

In this way, they will take 12.5 days to do 1 job.

Hope this helps.

Cheers


speedmaths.com


PS.
There is actually a PSLE Maths book that has 4 chapters to teach students how to solve such/similar Maths questions.
.

[MathIzzzFun]

ozora:

MathIzzzFun:

[quote=\"whitety\"]Hi, need help on 2 qns.


2) Huiling had 160 less marbles than George. George gave 75% of his marbles to Huiling. Huiling then gave 20% of her marbles to George. If Huiling had 192 more marbles than George in the end, how many marbles did Huiling have at first?

Thanks!

At first,
Huiling --> 16u
George --> 16u + 160 --- 75% = 12u + 120

After George gave 75% to Huiling
Huiling --> 28u + 120 -- 20% = 5.6u + 24
George --> 4u + 40

After Huiling gave 20% to George
Huiling --> 22.4u + 96
George --> 9.6u + 64
Huiling had 192 more, so
9.6u + 64 + 192 = 22.4u + 96
4u --> 50

at first, Huiling --> 200

cheers.

Sorry may I know how to get 16units for huiling n 12units +120 for75%?[/quote]One can start with 1 unit or 10 unit but the working will involve fraction/decimal; 16 units was chosen cos it \"matches\" 160 and is divisible by 4.

75% of (16 units + 160) = 3/4 x (16 unit + 160)= 3/4 x 16 + 3/4 x 160 = 12 + 120

cheers.

[ozora]

[

At first,
Huiling –> 16u
George –> 16u + 160 — 75% = 12u + 120

After George gave 75% to Huiling
Huiling –> 28u + 120 – 20% = 5.6u + 24
George –> 4u + 40

After Huiling gave 20% to George
Huiling –> 22.4u + 96
George –> 9.6u + 64
Huiling had 192 more, so
9.6u + 64 + 192 = 22.4u + 96
4u –> 50

at first, Huiling –> 200

cheers.[/quote]
Sorry may I know how to get 16units for huiling n 12units +120 for75%?[/quote]

One can start with 1 unit or 10 unit but the working will involve fraction/decimal; 16 units was chosen cos it "matches" 160 and is divisible by 4.

75% of (16 units + 160) = 3/4 x (16 unit + 160)= 3/4 x 16 + 3/4 x 160 = 12 + 120

cheers.[/quote]
thanks. I have tried using 1 unit and working really involved alot of fractions. THanks for sharing the method.

[Robertpattinsonidle]

what is the solution for these questions?


A rectangle tank was empty at first. Tap A was turned at a rate of 6 litres per min. After 2 min, B drain water at 2liters per min. Both tap turned off after 6 min after Zb was turned on. The tank was 28 cm in height and hold 56 litres find the height of water level in tank when both tank turn off.

Isaac read a book. 1st day he read 2/5 of it unread. 2nd day he read another 24 page of the book . In the end he read was 5/9the pages did not read. If he finish the rest in 4 days. What was the average number he read for the rest of the book?