InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
The first term of an AP is -5 and the last term is 45. If the sum of the terms of the AP is 120, then find the number of terms and the common difference. |
|
Answer» Let the first term, common difference and the number of terms of an AP are a, d and n respectively. Given that, first term (a) = - 5 and last term `(l)` = 45 Sum of the terms of the AP `= 120impliesS_(n)=120` We know that, if last term of an AP is known, jthen sum of `n` terms of an AP is, ` " " S_(n)=(n)/(2)(a+l)` `implies 120 =(n)/(2)(-5+45)implies12xx2=40xxn` `implies n=3xx2impliesn=6` ` :.` Number of terms of an AP is known, then teh `n`th term of an AP is, ` l =a+(n-1)dimplies45= -5+(6-1)d` `implies 50=5dimpliesd=10` So, the common difference is 10. Hence, number of terms and the common difference of an AP are 6 and 10 respectively. |
|