The ratio of the number of rambutan trees to the number of mango trees
was 5:3. After 12 more rambutan trees were planted, the new ratio became 11:6
How many mango trees were there?
R==Rambutan trees, M==Mango trees
R / M ==5 / 3.....................(1)
[R + 12] / M ==11 / 6..........(2)
From (1) above, we have:
M ==3R / 5
Substitute for M in ( 2) above:
[R + 12] / [3R / 5] ==11 / 6
Solve for R:
(5 (R + 12))/(3 R) = 11/6
Cross multiply:
30 (R + 12) = 33 R
Expand out terms of the left hand side:
30 R + 360 = 33 R
Subtract 33 R + 360 from both sides:
-3 R = -360
Divide both sides by -3:
R = 120 - Number of Rambutan trees
Sub into (1) above:
120 / M ==5 / 3
Cross multiply
5M ==360
M ==360 / 5
M ==72 - Number of Mango trees
