find the sum of all counting numbers between 50 and 350 that have 1 as the last digit.
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Answered by
0
The sequence 51+61+71...+341 is an arithmetic progression.
⇒ To find the sum of n terms of an AP we use the formula.
⇒ Here, n=30,a=51 and d=10.
∴ S
n
=
2
n
[2a+(n−1)d]
∴ S
n
=
2
30
[2×51+(30−1)10]
∴ S
n
=15[102+290]
∴ S
n
=15×392
∴ S
n
=5880
Answered by
0
Answer:
5880
The sequence 51+61+71...+341 is an arithmetic progression.
⇒ To find the sum of n terms of an AP we use the formula.
⇒ Here, n=30,a=51 and d=10.
∴ S
n
=
2
n
[2a+(n−1)d]
∴ S
n
=
2
30
[2×51+(30−1)10]
∴ S
n
=15[102+290]
∴ S
n
=15×392
∴ S
n
=5880
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