JEE Advanced Model Paper 16 with solutions for online practice

Let A, B,C denote x, y, z coins respectively ⇒ x + y + z =10
Coefficient of t10 in (1 + t + .... + t6) (1 + .... + t7) (1 + t + .... + t8)
= (t7−1)(t8−1) (t9−1)(1−t)−3
= (t7+t8+t9−1) (1−t)−3 (other terms are neglected)
= (

5

‌

C3 +

4

‌

C2 +

3

‌

C1 -

12

‌

C10)
= 47