Q&A - PSLE Math

[Leah_]

Hi! Need help with this qns. Thanks!

Peter had some $2 notes and $5 notes. He spent 50% of the $2 notes and 3/5 of his $5 notes. The value of the $2 notes left was the same as the value of the $5 notes left. The difference between the value of the $2 notes and the value of the $5 notes he had at first was $45. How much did Peter have at first?

[Ender]

vvv
A: 1705617
Subject: Math
Level: P6
Tags: Fraction, Percentage, u and p
Source:
^^^
At first, Let the number of $2 notes be 2u. And the number of $5 notes be 5p

Value of $2 notes = 2u X $2 = $4u
Value of $5 notes = 5p X $5 = $25p
$25p - $4u = $45 -----(1)

After spending 1/2 of $2 notes and 3/5 of $5 notes, value of $2 notes and $5 notes left are the same.
$2u = $10p
Substitute (2u=10P) into (1)

$25p - $20p = $45
p = 9

2u = 10p
2u = 90
u = 45

At first,
Value of $2 notes = $4u = $180
Value of $5 notes = $25p = $225

Total at first = $180 + $225 = $405

[ninjamathtv]

Sorry, 2 more. Many tks and God Bless:)

2) Three children, Sally, Lynn and Penny have different amounts of money.
The amount of money Lynn has is the total of Sally and Penny's amount.
The amount of money Penny has is the total of Sally's amount and half of Lynn's amount, Sally has $14.
(a) How much does Lynn have?
(b) How much do these three children have altogether?

This question can be easily solved by using the bar model method, part and whole concept. Watch the step by step video below:

[/youtube]

[sushi88]

Hi! Need help with this qns. Thanks!

Peter had some $2 notes and $5 notes. He spent 50% of the $2 notes and 3/5 of his $5 notes. The value of the $2 notes left was the same as the value of the $5 notes left. The difference between the value of the $2 notes and the value of the $5 notes he had at first was $45. How much did Peter have at first?

An alternative solution:

<---$-left----><----$-spent-------->
---<--50%-->
$2 (----2u----)(------2u-----)<-45-> <----$45 is the difference at first
$5 (--u--)(-u-)(--u--)(--u---)(--u---)
----<-- 2/5--><--------3/5--------->

Hence u-> 45
Peter has 9u at first => 9x45 = $405

[Nickal]

Hi, anyone can help? Tks in advance.

The ratio of the number of Larry's marbles to the number of John's marbles was 3:5. In a game with their friends, Larry won 15 marbles while John lost 3 marbles. They both then had the same number of marbles. How many marbles did both boys have altogether before the game?

[sushi88]

Hi, anyone can help? Tks in advance.

The ratio of the number of Larry's marbles to the number of John's marbles was 3:5. In a game with their friends, Larry won 15 marbles while John lost 3 marbles. They both then had the same number of marbles. How many marbles did both boys have altogether before the game?

Time--------Larry----John
Before--------3u-------5u
After--------3u+15-----5u-3

3u+15=5u-3
2u=18
u=9
Before total is 8u..Hence 8x9=72 marbles

[Nickal]

That's a great help! Tq!

[ninjamathtv]

Hi, anyone can help? Tks in advance.

The ratio of the number of Larry's marbles to the number of John's marbles was 3:5. In a game with their friends, Larry won 15 marbles while John lost 3 marbles. They both then had the same number of marbles. How many marbles did both boys have altogether before the game?

To make this question easier to understand, you can draw bar models like the video below:

[/youtube]

[Dr.Ta]

vvv
A: 1696145
Subject: {Math}
Level: {P6}
Tags: {Speed}
Source: {}
^^^

At 24min(o.4hr), Peter reached. meaning dave covered 2km lesser in 0.4hr.

therefore distance between town a n b = 0.4 x 70 + 2=30km

Peter speed = 30/0.4 hr = 75km/h

[Ender]

vvv
A: 1696145
Subject: {Math}
Level: {P6}
Tags: {Speed}
Source: {}
^^^

At 24min(o.4hr), Peter reached. meaning dave covered 2km lesser in 0.4hr.

therefore distance between town a n b = 0.4 x 70 + 2=30km

Peter speed = 30/0.4 hr = 75km/h

Your solution completely ignore the "6 minutes after they pass each other". If you considered this information, the whole question is flawed.