Let the number should be multiplied be X
Given number = 9 4/5
⇛ (9×5+4)/5
⇛ (45+4)/5
⇛ 49/5
On multiplying 49/5 with X then the result
= (49/5)×X
= 49X/5
According to the given problem
The result = 42
⇛ 49X/5 = 42
⇛ 49X = 42×5
⇛ 49X = 210
⇛ X = 210/49
⇛ X = 30/7
⇛ X = 4 2/7
Answer↓
The required number is 30/7 or 4 2/7
Check↓
On multiplying 4 9/5 with 4 2/7
⇛ 4 9/5 × 4 2/7
⇛ (49/5)×(30/7)
⇛ (49×30)/(5×7)
⇛ 7×6
⇛ 42
Verified.