leng2005 wrote: I post this the second time.Please help me.

cheers.

Academic support for Primary 5

- MathIzzzFun
- KiasuGrandMaster
**Posts:**2358**Joined:**Wed Mar 09,**Total Likes:**5

Post
by **MathIzzzFun** » Tue May 06, 2014 12:34 am

leng2005 wrote: I post this the second time.Please help me.

cheers.

Post
by **fire_fly** » Tue May 06, 2014 11:10 am

Cd you plus help....

From Red swastika sa12013:

The ratio of the age of Mdm Huda to her son's age is 5:1 now. In 7 years time, she would be thrice as old as her son. What is the total age of Mdm Huda and her son now?

Thank you. ...

From Red swastika sa12013:

The ratio of the age of Mdm Huda to her son's age is 5:1 now. In 7 years time, she would be thrice as old as her son. What is the total age of Mdm Huda and her son now?

Thank you. ...

- homeworkgurusg
- YellowBelt
**Posts:**20**Joined:**Mon Apr 28,

Post
by **homeworkgurusg** » Tue May 06, 2014 1:17 pm

Before ratio --> H : S = 5 : 1 (difference 4u)fire_fly wrote:Cd you plus help....

From Red swastika sa12013:

The ratio of the age of Mdm Huda to her son's age is 5:1 now. In 7 years time, she would be thrice as old as her son. What is the total age of Mdm Huda and her son now?

Thank you. ...

After ratio --> H : S = 3 : 1 (difference 2u)

Age difference between Mdm Huda and her son is unchanged after 7 years

So make the difference same

After ratio (x2) --> H : S = 6 : 2 (difference 4u now, same as before)

1u (6u-5u) --> 7 years

Age of Mdm Huda now is 5u --> 5x7=35

Age of her son now is 1u --> 7

Hope this helps.

Cheers

Post
by **Sruthi** » Tue May 06, 2014 5:26 pm

Hi ,

Can you please with the below question ?

Box A and Box B have the same shape and mass.6/7 of Box A and 2/5 of Box B are filled with sand . The mass of Box B with its contents is 7/10 the mass of Box A with its contents. The total mass of the

two boxes with their contents is 680 kg . Find the mass of a empty box .

Thanks.

Can you please with the below question ?

Box A and Box B have the same shape and mass.6/7 of Box A and 2/5 of Box B are filled with sand . The mass of Box B with its contents is 7/10 the mass of Box A with its contents. The total mass of the

two boxes with their contents is 680 kg . Find the mass of a empty box .

Thanks.

- speedmaths.com
- BrownBelt
**Posts:**559**Joined:**Mon Oct 12,**Total Likes:**3

Post
by **speedmaths.com** » Tue May 06, 2014 6:17 pm

Hi Sruthi,Sruthi wrote:Hi ,

Can you please with the below question ?

Box A and Box B have the same shape and mass. 6/7 of Box A and 2/5 of Box B are filled with sand . The mass of Box B with its contents is 7/10 the mass of Box A with its contents. The total mass of the two boxes with their contents is 680 kg .

Find the mass of anempty box .

Thanks.

Let's try;

You may use the "

6/7 of Box A and 2/5 of Box B are filled with sand.

30/35 of Box A and 14/35 of Box B are filled with sand.

Box A contains 30 Bags of sand

Box B contains 14 Bags of sand

The mass of Box B with its contents is 7/10 the mass of Box A with its contents.

Ratio of Box A with its contents to B with its contents is 10:7

Ratio of (Box A + 30 Bags) to (Box B + 14 Bags) is 10:7

Cross multiply:

7 Boxes + 210 Bags → 10 Boxes 140 Bags

210 Bags → 3 Boxes 140 Bags

70 Bags → 3 Boxes

The total mass of the two boxes with their contents is 680 kg .

(Box A + 30 Bags) + (Box B + 14 Bags) → 680 kg

2 Boxes + 44 Bags → 680 kg

70 Bags →3 Boxes

1 Bag → 3/70 Box

44 Bags → 44 x (3/70) Boxes

2 Boxes + 44 Bags → 680 kg

2 Boxes + [44 x (3/70) Boxes] → 680 kg

(Can you do this calculation?)

1 Box →

Hope this helps

Cheers

PS:

(1)

<<Mod's Note - ad removed : pls comply with our forum's ad posting rules>>

(2)

Some schools use “

Some schools use the algebraic version of “u” and “p”.

Students may use either version; whichever that they find easier.

.

Post
by **Sruthi** » Tue May 06, 2014 8:08 pm

I did not understand the below Cross multiply portion

Cross multiply:

7 Boxes + 210 Bags → 10 Boxes 140 Bags

210 Bags → 3 Boxes 140 Bags

70 Bags → 3 Boxes

Can you explain the how to do / why we do this step ?

Cross multiply:

7 Boxes + 210 Bags → 10 Boxes 140 Bags

210 Bags → 3 Boxes 140 Bags

70 Bags → 3 Boxes

Can you explain the how to do / why we do this step ?

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