Correct option is (b) five times the sum of its digits.
Let the digit be x and y
Given, the number of two digits is equal to six times the sum of its digits,
10x + y = 6(x + y)
⇒ 10x + y = 6x + 6y
⇒ 4x = 5y
⇒ \(x= \frac 54 y\)
Now, when the digits are reversed, the number will be 10y + x
Let 10y + x = a(x + y)
⇒ \(1 0y + \frac 54y = a (\frac 54y + y)\)
⇒ \(\frac{45}4 = a\frac 94\)
⇒ \(a = 5\)
Hence, if the digits are reversed the number so formed is equal to five times the sum of its digits.