Question

There are 5 different pairs of gloves, where left and right are distinguishable. Select 4 of the 10 gloves. (a) How many are there to select 2 pairs of gloves? (b) How many ways are there to select 4 gloves out of the 10 such that 2 of the 4 make a pair. (a pair consists of any right glove and left glove.)

Answer 1

Answer:

(a) How many are there to select 2 pairs of gloves?

10 ways

(b) How many ways are there to select 4 gloves out of the 10 such that 2 of the 4 make a pair. (a pair consists of any right glove and left glove.)

130 ways

Step-by-step explanation:

We solve the above questions using Combination

Combination = C(n, r) = nCr

= n!/n! ×(n - r)!

(a) How many are there to select 2 pairs of gloves?

We have 5 pairs of gloves. Therefore, the number of ways to select 2 gloves =5C2

= 5!/2! × (5 - 2)!

= 5!/2! × 3!

= 5 × 4 × 3 × 2 × 1/(2 × 1) × (3 × 2 × 1)!

= 10 ways.

(b) How many ways are there to select 4 gloves out of the 10 such that 2 of the 4 make a pair. (a pair consists of any right glove and left glove.)

We are told to select 4 gloves out of the 10 gloves = 10C4

We have 5 pairs, we need to make sure that two out of the selected 4 make a pair = 5 × 2⁴

= 80

Hence,

10C4 - 5C4

= [10!/4! × (10 - 4)!] - 80

= 210 - 80

= 130 ways