C15 + C25 +C35+C45+C55 এর মান কত?
A
16
B
32
C
31
D
33
Correct Answer: 31
5C1 + 5C2 + 5C3 + 5C4 + 5C5= (5÷1) + (5×4)÷2 + (5×4×3)÷(3×2)+(5×4×3×2)÷(4×3×2) + (5×4×3×2×1) ÷ (5×4×3×2×1)= 5 + 10 + 10 + 5 + 1= 31