CameraIcon
CameraIcon
SearchIcon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

In an AP if a=1, an=20 and Sn=399, then n is

A
19
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
21
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
38
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
D
42
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

The correct option is B 38
a=1
an=20
Sn=399
Then,
an=a+(n1)d
20=1+(n1)d
19=(n1)d
Also given,
Sn=n2×[2a+(n1)d]
Substituting values,
399×2=n(2+19)
798 = n×21
n=38

flag
Suggest Corrections
thumbs-up
5
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
MATHEMATICS
Watch in App
Join BYJU'S Learning Program
CrossIcon