Can someone please help with the following qtn, my answer is (1) but my teacher's answer is (2)? Please advise, thank you!


http://i62.tinypic.com/24b0u4k.jpg\">

alfretztay:

S-H:

Hi, can someone please help the following question. Thanks!


Two barrels X and Y contained different amounts of oil at first. Some oil from X was poured into y so that the amount of oil in Y was doubled. Then some oil from Y was poured into X so that the amount of oil in X was doubled. Finally, the barrels each contained 18 litres of oil. How many litres of oil were in X at first?

I would solve this problem by 'working backwards'.

X : Y : Total
At end, 18 : 18 : 36
-9 +9
------------ ---------
9 : 27 : 36
+13.5 -13.5
------------- ---------
At first, 22.5 : 13.5 : 36
Ans : 22.5 litres.

:thankyou: alfretztay & Kangkangteo

Kangkangteo:

S-H:

Hi, can someone please help the following question. Thanks!


Two barrels X and Y contained different amounts of oil at first. Some oil from X was poured into y so that the amount of oil in Y was doubled. Then some oil from Y was poured into X so that the amount of oil in X was doubled. Finally, the barrels each contained 18 litres of oil. How many litres of oil were in X at first?

X |___||___||___||___|18
Y |___||___||___||___| 18

4u ---> 18
1u ---> 18/4 = 4.5
---------------------

X |___||___|
Y |___||___||___||___||___||___|
---------------------

X |___||___||___||___||___|
Y |___||___||___|

5u ---> 4.5 x 5 = 22.5 litres (ans)

Confused :? Need further explanation please, thank you!

Hi, can someone please help the following question. Thanks!


Two barrels X and Y contained different amounts of oil at first. Some oil from X was poured into y so that the amount of oil in Y was doubled. Then some oil from Y was poured into X so that the amount of oil in X was doubled. Finally, the barrels each contained 18 litres of oil. How many litres of oil were in X at first?

edlynnalexander:

S-H:

Hi, please help the following qtn:


Lisa has some apples and pears in a basket. If she buys 10 apples, 3/5 of the fruits in the basketare pears. If she buys 30 pears, 3/4 of the fruits in the basket are pears. How many apples are there in the basket?

http://i58.tinypic.com/i4empf.png\">

:thankyou:

NGU Learning:

S-H:

Hi, please help the following qtn:


Lisa has some apples and pears in a basket. If she buys 10 apples, 3/5 of the fruits in the basketare pears. If she buys 30 pears, 3/4 of the fruits in the basket are pears. How many apples are there in the basket?

Apples: 2 units - 10 = 1 part
Pears: 3 units = 3 parts - 30

3 units = 6 units - 30 - 30
3 units = 60
1 unit = 20

Number of apples = 2 * 20 - 10 = 30 apples

Thank you NGU Learning, but I am still confuse with your working! Can u please explain again? Thanks

Hi, please help the following qtn:


Lisa has some apples and pears in a basket. If she buys 10 apples, 3/5 of the fruits in the basketare pears. If she buys 30 pears, 3/4 of the fruits in the basket are pears. How many apples are there in the basket?

Kangkangteo:

S-H:

Hi, can someone please help with the following qtns, thanks!

1)
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2)
http://i60.tinypic.com/k1fo21.jpg\">

3)
http://i62.tinypic.com/52lx5z.jpg\">

My answers are 3, 4, 4

:thankyou:

Hi, can someone please help with the following qtns, thanks!

1)
http://i60.tinypic.com/21e59x4.jpg\">

2)
http://i60.tinypic.com/k1fo21.jpg\">

3)
http://i62.tinypic.com/52lx5z.jpg\">

Kangkangteo:

S-H:

Can someone help me with the following qtn with the \"backwards method\", thank you:-


John and Mary had some cookies at first. John gave 2/7 of his cookies to Mary. In return, Mary gave 1/4 of her cookies to John. In the end, John and Mary had the same number of cookies. What was the ratio of John's cookies to Mary's cookies at first?

J [___][___][___]
M [___][___][___]

-------------
J [_][_][_][_][_]
J [_____][_____]
M [_____][_____][_____][_____]
M [_][_][_][_][_] [_][_][_][_][_]

-------------
J [_][_][_][_][_][_][_]
M [_][_][_][_][_][_][_][_]

The ratio of John's cookies to Mary's cookies at first was 7 : 8.

Thank you!