1
You visited us
1
times! Enjoying our articles?
Unlock Full Access!
Byju's Answer
Standard X
Mathematics
nth Term of an AP
The A.P. in w...
Question
The A.P. in which 4
th
term is –15 and 9
th
term is –30. Find the sum of the first 10 numbers.
Open in App
Solution
It is given that,
t
4
= –15
t
9
= –30
Now,
t
n
=
a
+
n
-
1
d
t
4
=
a
+
4
-
1
d
⇒
-
15
=
a
+
3
d
⇒
a
=
-
15
-
3
d
.
.
.
1
t
9
=
a
+
9
-
1
d
⇒
-
30
=
a
+
8
d
⇒
a
+
8
d
=
-
30
⇒
-
15
-
3
d
+
8
d
=
-
30
from
1
⇒
-
15
+
5
d
=
-
30
⇒
5
d
=
-
30
+
15
⇒
5
d
=
-
15
⇒
d
=
-
3
⇒
a
=
-
15
-
3
-
3
from
1
⇒
a
=
-
15
+
9
⇒
a
=
-
6
Hence, the given A.P. is –6, –9, –12, ....
Now,
S
n
=
n
2
2
a
+
n
-
1
d
S
10
=
10
2
2
a
+
10
-
1
d
=
5
2
-
6
+
9
-
3
=
5
-
12
-
27
=
5
-
39
=
-
195
Hence, the sum of the first 10 numbers is –195.
Suggest Corrections
29
Similar questions
Q.
Find the sum of first
17
terms of an
A
.
P
.
, where
4
t
h
and
9
t
h
terms are
−
15
and
−
30
, respectively.
Q.
Find the sum of first
17
terms of an AP whose
4
t
h
and
9
t
h
terms are
15
and
30
respectively.
Q.
Question 27
Find the sum of first 17 terms of an AP whose
4
t
h
and
9
t
h
terms are – 15 and –30, respectively.
Q.
Question 27
Find the sum of first 17 terms of an AP whose
4
t
h
and
9
t
h
terms are – 15 and –30, respectively.
Q.
Find the sum of first 15 terms of an A.P. whose 5th and 9th terms are 26 and 42 respectively
View More
Join BYJU'S Learning Program
Grade/Exam
1st Grade
2nd Grade
3rd Grade
4th Grade
5th Grade
6th grade
7th grade
8th Grade
9th Grade
10th Grade
11th Grade
12th Grade
Submit
Related Videos
General Form of an AP
MATHEMATICS
Watch in App
Explore more
nth Term of an AP
Standard X Mathematics
Join BYJU'S Learning Program
Grade/Exam
1st Grade
2nd Grade
3rd Grade
4th Grade
5th Grade
6th grade
7th grade
8th Grade
9th Grade
10th Grade
11th Grade
12th Grade
Submit
AI Tutor
Textbooks
Question Papers
Install app