Q&A - PSLE Math

[MathIzzzFun]

Winx5015:

Hi, need help for the following questions.


(2). If Allan and Bob work together, they can complete a job in 12 days. If they work together for 3 days, followed by Bob who worked alone for the next 5 days, they can finish 5/12 of the job. How many days will each of them need to complete the job if they were to work alone?

Thanks!

Hi

Q2.
Allan & Bob --- 12 days --> 12 units of work
Allan & Bob -- 3 days --> 3 units of work

Bob -- 5 days --> 5-3 = 2 units of work
Bob -- 12 units of work --> 12/ 2 x 5 = 30 days

Allan & Bob --- 5 days --> 5 units of work
Allan -- 5 days --> 5 - 2 = 3 units of work
Allan -- 12 units of work --> 12 /3 x 5 = 20 days

cheers.

[tianzhu]

Hi kklau


Good Morning.

What I am sharing is one similar question which my kid had done years ago.

If the question is shaded as I’ve drawn, then you may follow the steps as shown in this slide.I've attempted to breakdown the composite figure into familiar shapes.Please get your child to work out the other details.

Please take note that this is a possible way, there are alternatives.

Usually, the calculations in questions on composite figures are quite neat, just applying the formulae and pressing the calculators. But, the difficulties many students faced are visualising and rearranging the shapes into familiar shapes. This is the part which tripped many students.

You may also refer to small’s solution.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7041/7154653294_de8b0cc591_z.jpg\">

[tianzhu]

Winx5015:

(2). If Allan and Bob work together, they can complete a job in 12 days. If they work together for 3 days, followed by Bob who worked alone for the next 5 days, they can finish 5/12 of the job. How many days will each of them need to complete the job if they were to work alone?

Hi

Good Morning.

A similar question has been discussed before.

Hope this helps.

Best wishes.

http://farm5.staticflickr.com/4053/4715375219_19cfa8eb65_z.jpg\">

[Winx5015]

Thanks speedmaths.com , MathIzzzFun and tianzhu for your solutions.


Really appreciate your help

[tianzhu]

superhappy:

Hi, need help on this questions
1. Varsha had some 20-cent and 50-cent coins.
7/8 of the coins were 20-cent coins and the rest were 50-cent coins.
After Varsha had spent $72.50 worth of 50-cent coins and 5/7 of the 20-cent coins, she had 2/7 of coins left. Find the total amount of money Varsha left.

Hi

This question has been discussed before.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7054/6835330158_899602206e_z.jpg\">

[tianzhu]

superhappy:

2. The ratio of the number of beads John had to the number of beads Sally had was 3:7 at first. After Sally had given some beads to John, Sally had 76 beads less than John. The ratio of John's number of beads to Sally's number of beads became 3:2.
a) how many beads did Sally give to John?
b) what percentage of her beads did Sally give to John?

Hi

A student should take note the total number of beads remains the same in the before and after scenarios.

You may work with MD or UM (Units Method).

Before
John:Sally ------ 3:7

After
John:Sally ------ 3:2 -------6:4 (Use equivalent ratios, make the total number of units the same)

2 units ------- 76
1 unit ------ 38

a) Sally gave 3 units or 3*38 (114) to John

b) 3/7*100% ------42.86%

Hope this helps.

Best wishes

[Michaelia0816]

rose michelle:

The figure below shows 3 different rectangles, X, Y ad Z. 3/10 of X and 40% of Z is shaded. The shaded area of X is the same as the shaded area of Z. What fraction of the figure is unshaded if 60% of Y is shaded?

Can post the figure, I am not sure about Y. The question did not say about rectangle Y.

[Michaelia0816]

Notes:

30% of X is 40% of Z
100% of X is 133/1/3 of Z

[Michaelia0816]

Need help with this following questions, Tianzhu, pls give me step by step answer and helps me into understanding as tomorrow will be my SA1 Math.



7) The amount of water in a tank is between 120 litres and 190 litres. If I use the water to fill up containers each with capacity of 6 litres, there will be 1 litres left over.
But if I use the water to fill up containers each with 7 litres, these will be 3 litres left over. How much water was there in the tank?

[Michaelia0816]

12) An empty cup was 75g. A cup with objects A and B was 300g. A cup with objects A and C was 375g. A cup with objects B and C was 350g


A) What was the total mass of objects A,B and C?
B) Find the mass of object A?