Discussion

Explanation:

Let the number be ‘ab’.

Sum of the digits i.e., a + b = 7   …(1)

Difference of the digits is 1.

Now we don’t know out of a and b which is greater, hence, we’ll have to make two cases.

Case 1: a ≥ b

⇒ a – b = 1   …(2)

Solving equations (1) and (2) we get,

a = 4 and b = 3.

Hence, the number is 43.

Case 1: b ≥ a

⇒ b – a = 1   …(3)

Solving equations (1) and (3) we get,

a = 3 and b = 4.

Hence, the number is 34.

Now the smallest such number is clearly 34.

Hence, 34.

» Your doubt will be displayed only after approval.