KEAM 2017 Math Paper

We have, 4 red, 2 white and 4 black balls.
∴ Total balls =4+2+4=10
Number of ways of selecting 4 balls from 10 balls =‌10C4
∴‌‌n(S)=‌10C4
Let E= Event getting 2 red balls
∴‌‌n(E)=‌4C2×‌6C2
∴ Required probability =p(E)
=‌

n(E)

n(S)

=‌

‌4C2×‌6C2

‌10C4

=‌

‌ 4×3 2×1 × 6×5 2×1

10×9×8×7 4×3×2×1

=‌

6×15

10×3×7

=‌

3

7

=‌

9

21