The number of natural numbers, between 212 and 999 , such that the sum of their digits is 15 , is

Step-by-step solution

Let the number be aligned & 2 a b, a+b=13 & a, b 0,9 & 6 numbers (9,4),(8,5) (4,9) aligned Similarly, for 3 a b, a+b=12 7 numbers For 4 a b, a+b=11 Numbers For 5 a b, a+b=10 9 numbers For 6 a b, a+b=9 10 numbers For 7 a b, a+b=8 9 numbers For 8 a b, a+b=7 8 numbers For 9 a b, a+b=6 7 numbers Total ways =64 .