
By: Petkwang (offline) Wednesday, January 18 2012 @ 08:36 PM CST (Read 1072 times)



Petkwang 
There are 830 mango and guava trees in a plantation. A fire destroyed 2/5 of the guava tree. 50 more mango trees were then planted. As a result, the number of mango trees in the plantation was 1/6 the number of guava trees. How many more guava trees than mango trees were there in the plantatuion at first?
Please use model to solve, thanks.

Newbie
Registered: 01/16/12 Posts: 3





By: Yingobi (offline) Wednesday, January 18 2012 @ 09:03 PM CST



Yingobi 
Hihi,
you can use before and after models to solve. Since we have no info abt the before model, we shld draw the after model first, which is 1 unit for the mango trees and 6 units for the guava trees.
then we know that 2/5 of the guava trees were destroyed, so only left w 3 units. the after model indicates tt the guava trees left is 6 units, so we should 'x2' to 2/5 to get 4/10. meaning total units for guava at first is 10units, 4 units were destroyed, left 6 units, which is now equal to the after model.
we can draw the before model now. add 4 units back to the guava trees and minus 50 from the mango trees which were planted. Equate total before model = 830.
Form relationship =>
11 units => 830 + 50
1 unit => 80
guava trees: 80 x 10 units = 800
mango trees: 80  50 = 30
more: 800  30 = 770 (ans)
HTH!

Newbie
Registered: 01/05/10 Posts: 1





By: Petkwang (offline) Thursday, January 19 2012 @ 06:26 PM CST



Petkwang 
Thank you.

Newbie
Registered: 01/16/12 Posts: 3



