Tutor MathsGuru: Ask me for your burning Maths questions!

[jieheng]

HVR:

Now I can explain to my kid. Thank you very much

Hi HVR ,

You are welcome .

Regards,

[MathIzzzFun]

wahwah:

HI,

Need help with the following math questions. Many thanks in advance.

A worker takes 9 hrs to build a wall while another worker takes 10 hr to build the same wall. When both workers work together, they sometimes stop for a chat and they lay 10 bricks fewer per hour than their total if they had worked seperately. If the two workers take 5 hours to build the wall together, how many bricks are needed for the wall?

I have six coins- three 5 cents coins and three 10 cents coins. I place two coins in each of three boxes labeled 10 cents, 15cents and 20cents in such a way that these are not the respective values of coins inside. What is the least number of coins you would have to remove, and from which box or boxes, so as to determine which coins are in which boxes? Write your explanation clearly.

Q1.
When the workers work separately,
in 1 hour, they would build 1/9 + 1/10 = 19/90 of the wall

When they work together, they lay 10 less bricks per hour and therefore could finish the wall in 5 hours ie they could complete only 1/5 of the wall in 1 hour

So 19/90 of wall - 10 bricks = 1/5 of wall

1/90 (= 19/90 - 1/5) of wall = 10 bricks ==> Full wall = 90 x 10 bricks = 900 bricks.

Q2.
There are only two ways to place the coins in the 3 boxes such that the value of coins in each box will not be the same as the label on the box.

Combination 1 - 10 cents box (5cents + 10cents), 15 cents box (10 cents + 10 cents), 20 cents box (5 cents + 5 cents)

Combination 2 - 10 cents box (10 cents + 10 cents), 15 cents box (5 cents + 5 cents), 20 cents box (5 cents + 10 cents)

So by removing one coin from the 15 cents box, one will be able to determine which coins are in which box. If it is a 5-cent coin > combination 2. If it is a 10-cent coin > combination 1.

cheers.

[SaPan]

Dear uncles/aunties,

pls help me with this question.

A group of children met for a table tennis game. Each child played with everyone else. Lisa played with thrice as many girls as boys. Bob played with 4 times as many girls as boys.

a. how many children were there altogether?
b. were there more boys or girls? how many more?

thank you in advance

[FrekiWang]

SaPan:

Dear uncles/aunties,

pls help me with this question.

A group of children met for a table tennis game. Each child played with everyone else. Lisa played with thrice as many girls as boys. Bob played with 4 times as many girls as boys.

a. how many children were there altogether?
b. were there more boys or girls? how many more?

thank you in advance

Model as follows:

Let one block be the number of boys

From the first condition,
number of girls = 3 blocks + 1 (Lisa)
From the second condition,
number of girls = [1 block - 1(Bob)] x 4 = 4 blocks - 4

3 blocks + 1 is the same as 4 blocks - 4, then 1 block represents 5.

Therefore there are 5 boys and 16 girls, do the rest of the working yourself:D

[softcoach]

Hi


Appreciate it very much if someone can help with this question. Thank you.


A cleaner had to wash all the cars parked at a multi-storey car park by the end of the day. In the morning, the number of cars he washed was 2/5 of the number of cars that was not washed yet. In the afternoon, he washed another 26 cars. As a result, the total number of cars washed became 4 fewer than 9/14 of the total number of cars at the car park. What was the total number of cars parked at the multi-storey car park?

[Yu Xuan]

softcoach:

Hi


Appreciate it very much if someone can help with this question. Thank you.


A cleaner had to wash all the cars parked at a multi-storey car park by the end of the day. In the morning, the number of cars he washed was 2/5 of the number of cars that was not washed yet. In the afternoon, he washed another 26 cars. As a result, the total number of cars washed became 4 fewer than 9/14 of the total number of cars at the car park. What was the total number of cars parked at the multi-storey car park?

Hi

Before;
Washed : Not Washed : Total
2 : 5 : 7
4 : 10 : 14

After; (total remain unchanged)
Washed --> 4u + 26
Not washed --> 10u - 26
Total --> 14u

4u + 26 + 4 = 9/14 of 14u
1u --> 6
14u --> 6 X 14 =84

Yu Xuan

[SoWoW]

Need help from the experts here…


A class of Chinese and Malay pupils went to the zoo. The ratio of the number of Chinese pupils to the number of Malay pupils was 10 : 7. The ratio of the number of Malay boys to the number of Malay girls was 9 : 5. What was the ratio of the number of Malay girls to the number of CHinese pupils in its simplest form?

Please help to confirm as the answer should be 1: 4 or 1:2??

[Yu Xuan]

SoWoW:

Need help from the experts here..


A class of Chinese and Malay pupils went to the zoo. The ratio of the number of Chinese pupils to the number of Malay pupils was 10 : 7. The ratio of the number of Malay boys to the number of Malay girls was 9 : 5. What was the ratio of the number of Malay girls to the number of CHinese pupils in its simplest form?

Please help to confirm as the answer should be 1: 4 or 1:2??

Hi

Chinese : Malay
10 : 7
20 : 14

Malay
Boys : Girls : Total
9 : 5 : 14

Malay Girls : Chinese
5 : 20
1 : 4

[Yu Xuan]

wahwah:

HI,

Need help with the following math questions. Many thanks in advance.

A worker takes 9 hrs to build a wall while another worker takes 10 hr to build the same wall. When both workers work together, they sometimes stop for a chat and they lay 10 bricks fewer per hour than their total if they had worked seperately. If the two workers take 5 hours to build the wall together, how many bricks are needed for the wall?

Hi, my two cents worth;

In 1h;
1st worker --> 1/9 wall/h -->10/90 wall/h
2nd worker --> 1/10 wall/h --> 9/90 wall/h
Total --> 19/90 wall/h

In 5h;
Number bricks fewer-> 5 X 10 = 50bricks

Time needed to complete the wall;
1 ÷ 19/90wall / h = 4 14/19h

Diff in time taken --> 5h – 4 14/19h = 5/19h

5/19h -->50 bricks
4 14/19h --> (50 ÷ 5/19 ) X 4 14/19h = 900 bricks

Yu Xuan

[Chan09]

Dear all,

Need help on the below questions:
1) a man is 4 times as old as his son. 4 years ago he was 6 times as old as his son. What is the present age of father and son (ans: 40 and 10 yrs old)

2) Lee bought 4 times as many toy cars as teddy bears. She spent $1750 altogether. A toy car cost $10 less than a Teddy bear. Total cost of toy car was $490 more than total cost of Teddy bears.
A) how much did lee spend on the Teddy bears? (ans: $630)
B) how much did one Teddy bear cost? $18

3) Lim was reading a book. On the first day, the number of pages he read was 2/5 of the number of pages unread. On the second day, he read another 24 pages. As a result, the number of pages he read was 5/9 of the number of pages unread. If he had to complete reading the book in another 4 days, what was the average number of pages he had to read a day for the rest of the book? ( ans: 54 pages)

Thank you in advance. :stupid: