Question

sum of the digits of two digit no. is 9

Answer 1

Answer is 18 I hope this is OK

Answer 2

Given, Sum of the digits of two digit number is 9.

Let the digits be x, y and number is xy.

So, If

• x = 1, y = 8
• x = 2, y = 7
• x = 3, y = 6
• x = 4, y = 5
• x = 5, y = 4
• x = 6, y = 3
• x = 7, y = 2
• x = 8, y = 1
• x = 9, y = 0

Therefore, The numbers will be 18, 27, 36, 45, 54, 63, 72, 81, 90

b)Total numbers formed = 9

All the numbers are divisible by 9, (Sum of digits = 9) Hence divisible by 3

Hence divisible by 318,36, 54, 72, 90 are divisible by 2 also.

Probability that a number is divisible by 3 and 2 = 5/9.

c) Total numbers = 9

All numbers are divisible by either 2 or 3.

Probability that a number is divisible by 2 or 3 = 9/9 = 1

Only concept we used is, $\boxed{ \sf Probability = \frac {Favorable \: outcomes} {Total \: outcomes} }$