Question

Some children were going to the Computer Room. The first time there was a knock at the door, 1 child entered the Computer Room. On each of the followings knocks, the group that entered had 2 more children in it than the group that entered at the previous knock. All the children had entered the room on the tenth knock. how many children are there in the Computer Room?

Answer 1

they're 100 children in the computer room

Explanation:

1+3+5+7+9+11+13+15+17+19=100

Answer 2

• 100 children

Explanation:

This situation describes the AP with:

• The first term of a₁ = 1
• Common difference d = 2

The nth term of AP is:

• aₙ = a₁ + (n - 1)d

The sum of the first n terms:

• Sₙ = (a₁ + aₙ)*n/2
• S₁₀ = (1 + 1 + 9*2)*10/2 = 20*5 = 100