9
Q:
A) 19 months | B) 21 months |
C) 18 months | D) 20 months |
Answer: B) 21 months
Explanation:
Explanation:
Total savings = 200 + 200 + 200 + 240 + 280 + ... to n months = 11040
= 120 + 80 + 160 + 40 + 200 + 240 + ....n terms
= 40 + 80 + 120 + 160 + 200 + 240 + ...n terms
= n/2[2a + (n-1)d] + 80 + 40 = 11040
= n/2[240 + (n-1)40] = 10920
= n[6+n-1] = 546
= n[n+5] = 546
n = 21