Permutation Combination Question 19

Question 19 - 01 February - Shift 2

Number of integral solutions to the equation $x+y+z=21$, where $x \geq 1, y \geq 3, z \geq 4$, is equal to ________

Show Answer

Answer: 105

Solution:

Formula: Selection Formula

${}^{15} C_2 = \frac{15 \times 14}{2} = 105$