There are 28 persons present at a press conference. After the conference they all shake hands with each other. If 7 of them
refuse to shake hands at all, then how many hands shakes will be there altogether?
This questions was previously asked in
SSC CGL 17th August 2021 Shift-3
Explanation:
- Total people: 28
- 7 refuse to shake hands, so 28 - 7 = 21 people shake hands.
- Each of the 21 shakes hands with the others: calculated using 21 choose 2.
- Formula for handshakes: \( \frac{21 \times 20}{2} = 210 \).
- Option:1, 378 - Incorrect; possibly 28 choose 2 without exclusions.
- Option:2, 231 - Incorrect; does not fit increment criteria.
- Option:3, 420 - Incorrect; double of correct option, likely error.
- Option:4, 210 - Correct answer for 21 people shaking hands.