KOOLMUM:

Hi


Please help to solve below question , thank u!

A jar filled with 40 identical screws weighs 1.4 kg.
The same jar when filled with 20 identical nails weighs 500g. The mass of each screw is twice the mass of each nail.

What is the mass of the empty jar?

[ Jar ] [ 40 x 2 = 80 nails] --> 1400g
[ Jar ] [ 20 nails] --> 500g

80 nails - 20 nails --> 1400g - 500g = 900g
20 nails --> 900g / 3 = 300g
Jar --> 500g - 300g = 200g

Yuxuan

marstolive:

Hi need speedy assistance!


A car and a van set off the same time on a 216km journey.
The car reached the destination 1.5 hours earlier than the van.
When the car completed the journey, the van was still 72 km away from the destination.
Find the speed of the car.
:rahrah:

TIA

Van's speed --> 72km / 1.5h = 48km/h
Van's Distance --> 216km - 72km = 144km
Van's Time --> 144km / 48km/h = 3h

Car's Time --> 3h
Car's Speed --> 216km / 3h = 72km/h

Yuxuan

Distance of HouseMouse –> 12km/h x 1/3h = 4km

Distance of Cheetah –> 4km + 36km = 40km
Distance of Pronghorn –> 4km + 28 2/3km = 32 2/3km

Speed of Cheetah –> 40km / 1/3h = 120km/h
Speed of Pronghorn –> 32 2/3 km / 1/3h = 98km/h

Average Speed –> [ 4km + 40km + 32 2/3km ] / [1/3h + 1/3h + 1/3h ]
= 76 2/3km/h approx equal to 77km/h

Is that the answer?
It is weird that the question should ask the average speed of all 3 mammals.

Yuxuan

megamage1000:

Hi, i have a hard time resolving this question, Hope you will help me!


In a photocopier shop, Copier A was turned on first, and it printed 240 pages.Then Copier B was turned on , and Copier A and Copier B continue printing together.For every 4 pages Copier A printed, Copier B printed 7 pages . Copier B printed 30 pages fewer than 2/7 of the total number of pages printed.

Find the total number of pages printed.

Hi

A --> 5 units + 30
B --> 2 units - 30
Total --> 7 units

By removing the 240 printed earlier by A, both machine worked for the same amount of time and hence we can relate their output to their respective speed ratio;
4 parts --> 5 units + 30 -240 = 5 units - 210
7 parts --> 2 units - 30

28 parts --> 35units - 1470
28 parts --> 8units - 120
draw a model to represent the 28 parts, you will see that,
27 units --> 1470 - 120 = 1350
1 unit --> 50
7 units --> 50 x 7 = 350

Yuxuan

bobsg01:

Math Problem again.


Thank you for any help rendered.

http://i52.tinypic.com/jt5ifb.jpg\">

Hi, I have a slightly different method for (b)

Diff. in delivery cost for 4 days --> ($170 - $58 ) x 4 = $448
Diff in per person for 4 days --> ($19.99 - $15.99) x 4 = $16

$448 ÷ $16 = 28 people per day
28 x 4 = 112 people in 4 days


Yuxuan

match3frog:

Hi, need help with this question:


Isaac 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 of the book. 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?

Thanks!

My first reply seems to have gotten lost...

1st Day
Read : Not Read
2 : 5
4 : 10

2nd Day
Read : Not Read
5 : 9

(Equate the total of both days since total number of pages should be the same.)

5units - 4 units --> 24
9 units --> 24 x 9 = 216
216 ÷ 4 = 54

ozora:

Hi all

I used algebra to solve this problem but is it possible to use model to solve the problem? If yes, how?
Twice of a number is greater than two-third of that number by 28.
I got the answer 21.
Thanks

Hi

Model is pretty easy to understand in this case;

Let the number be 3 units, hence twice the number will be 6 units, and 2/3 the number will be 2 units

[N][N][N][N][N][N]
[N][N]-----28 ------

4 units -->28
1 unit --> 28 ÷ 4 = 7
3 units --> 7 x 3 = 21

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

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

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