DRDO Multi tasking staff Model paper 5

Tips & Tricks
Let the numbers be 9a and 9b, since 9 is a common factor, a and b are coprime.
We know that 9a × 9b = H.C.F × L.C.M
⇒ 9a × 9b = 9 × 180
⇒ ab = 20
The possible values of a and b are: (1,20), (4,5).The corresponding values of the two numbers would be (9,180), (36,45).
Only 36 and 45 lie between 30 and 50, Therefore sum = 81.