Q&A - PSLE Math

[tianzhu]

Michaelia0816:

I got a hard question, pls help me .

There were a total of 20800 sacks of rice in warehouse x and y.after 3/4 of the stock in x and 3/5 in y were sold. There were 1040 more sacks of rice in y than x. How many sacks of rice were there in each warehouse at first?

Answer:
Warehouse X:_____
Warehouse Y:_____

Hi

This question looks familiar.

A neat way is to use MD.

Warehouse X

Left ------- 2 units
Sold ------- 6 units

Warehouse Y

Left ------- 2 parts
Sold ------- 3 parts

There were 1040 more sacks of rice in Y than X.

Hence, 1 part ------ 1 unit + 520

8 units + 5 units + 2600 ------- 20800

1 unit -------- 1400

X ------- 8*1400 ------- 11200

Y ------- 20800 – 11200 ------ 9600

Best wishes

[she0407]

Need help in this Q.


A fruit seller has 60 more oranges than apples. After he sold 75% of the oranges and 60% of the apples, he is left with 9 more apples than oranges.
(a) How many apples does he have at first?
(b) What fraction of the fruits left were oranges?

Thanks in advances!

[Maths Hub]

Let there be 4 units of oranges and 5 parts of apples

4 units ------------ 5 parts + 60
1 unit + 9 -------- 2 parts implies
4 units + 36 ----- 8 parts therefore
3 parts ----------- 96 apples
(a) apples at first 5 parts ----- 160 apples
(b) 64 apples left and 55 oranges left
55/119 of fruits left were oranges

[Michaelia0816]

Thanks, Tianzhu!!!

[AJH]

Thank you very much, 2cor41618 - your explanations are very clear.


I nd help with these questions:

1. At first, Ashley had 550 marbles altogether. There were 3/8 as many blue marbles as yellow marbles. Later, she bought some blue marbles. For every 4 yellow marbles she had, her father gave her 25 more yellow marbles. The total number of yellow marbles then became 1 and 2/3 times that of the blue marbles. How many blue marbles did she have in the end?

For this question,my workings so far:

11u - 550 marbles
1u - 50 marbles
8u - 400 marbles

400 yellow marbles - so, Ashley's father gave her 2500 more yellow marbles.

I'm stuck here. :scratchhead:

2. There are 4 adults. Each time, 2 adults are weighed, giving a total of 6 readings, in kg as listed below:

103.5, 111, 112.5, 117, 118, 122

What is the average mass of the 4 adults?

Thank you.

[Maths Hub]

.

[tianzhu]

AJH:

1. At first, Ashley had 550 marbles altogether. There were 3/8 as many blue marbles as yellow marbles. Later, she bought some blue marbles. For every 4 yellow marbles she had, her father gave her 25 more yellow marbles. The total number of yellow marbles then became 1 and 2/3 times that of the blue marbles. How many blue marbles did she have in the end?

For this question,my workings so far:

11u - 550 marbles
1u - 50 marbles
8u - 400 marbles

400 yellow marbles - so, Ashley's father gave her 2500 more yellow marbles.

I'm stuck here. :scratchhead:

Hi

At first, Ashley had 550 marbles altogether.

11 units ------ 550
1 unit ------ 50

Blue marbles -------- 150
Yellow marbles -------- 400

For every 4 yellow marbles she had, her father gave her 25 more yellow marbles.

Hence, for 400 yellow marbles, her father gave another 2500 yellow marbles.

In the end there are 2900 yellow marbles.

The total number of yellow marbles then became 1 and 2/3 times that of the blue marbles.

5 parts ------- 2900

1 part ------- 580

3 parts ------- 1740 (blue marbles in the end)

Best wishes

[tianzhu]

AJH:

2. There are 4 adults. Each time, 2 adults are weighed, giving a total of 6 readings, in kg as listed below:

103.5, 111, 112.5, 117, 118, 122

What is the average mass of the 4 adults?

Thank you.

Hi

Let call the 4 adults, A,B,C and D.

They can be grouped as such for the weighing sessions. This’ll give us 6 readings.

AB
AC
AD

BC
BD

CD

So, you can see there are 3 groups of (A+B+C+D)

A+B+C+D ------- (103.5+111+112.5+117+118+122)/3

A+B+C+D ------- 228

Hence the average is 228/4 -------- 57

Best wishes

[dicoyote]

A group of pupils calculated their average score for a class test. They found that if one of them scored another 22 marks, their average mark would be 90. However, if one of them scored 8 marks less, their average mark would be 80. How many pupils were there in the group?


Thanks in advanced

[2cor41618]

dicoyote:

A group of pupils calculated their average score for a class test. They found that if one of them scored another 22 marks, their average mark would be 90. However, if one of them scored 8 marks less, their average mark would be 80. How many pupils were there in the group?


Thanks in advanced

Let the number of pupils be 1u.

If one of them score 22 marks more, the average is 90. This means that the total will b 90x 1u -22=90u -22.

If one of them score 8 marks less, the average will b 80. This means that the total is 80u +8.

Therefore, 90u-22=80u+8
10u=30
1u=3

Ans:3 pupils