Math, asked by abhilashlamani1, 1 month ago

if the sum of 7th and 12 th term of Ap is 42 the the sum of its first 18 term is

Answers

Answered by EvilRage

2

Answer:

378

Step-by-step explanation:

7th term = a+6d

12th term = a+11d (using a+(n-1)d)

a+11d+a+6d=42

2a+17d=42 - - - (1)

Sum of 18 terms n/2(2a+(n-1)d)

18/2(2a+(17d))

9(42)

=378

Previous Question

Next Question

Similar questions

Math, 15 days ago

a box contains 12 balls out of which 10 are black and 2 are white what is the probability the 3 are black and 2 white...

History, 15 days ago

write a short note on ghiyasuddin balban.

Hindi, 15 days ago

do join yyx imom jxa...

Chemistry, 1 month ago

Derive an expression for magnetic field at any point on the axis of a circle current loop by applying Biot-Savart's Law.

Math, 1 month ago

if x^3+y^3=133 and x^2-xy+y^2=19 then the value of x+y is?

Math, 9 months ago

$2 - \sqrt5{6}$ Solve this and become brainliest...

History, 9 months ago

describe the land revenue policy by Akbar...

Social Sciences, 9 months ago

what dose the universe consists of...