Question

A tower buikd with cards only 2 cards are needed for 1 floor and 7 cards are needed for 2 floors an so on what is the number of cards needed for 10 floors

Answer 1

Answer:

155 cards needed for 10 floors

Step-by-step explanation:

Cards Needed for one floor = 1

a = 2

Card needed for two floors = 7

Sn = (n/2)(a + a + (n-1)d)

S₂ = (2/2)(2 + 2 + (2-1)d)

S₂ = 7

7 = (2/2)(2 + 2 + (2-1)d)

7 = 1 × (4 + d)

7 = 4 + d

d = 3

S₁₀ = (10/2)(a + a + (10-1)d)

S₁₀ = 5 × (2 + 2 + 9×3)

S₁₀ = 5 × (4 + 27)

S₁₀ = 5 × 31

S₁₀ = 155

155 cards needed for 10 floors