#### An arithmetic progression has first term a and common difference 3. The sum of the first 50 terms is 5200.

a =?

Anonymous

0

a =?

Krishna

0

Step 1: Note down the given terms, and recall the formula for sum of n terms of an arithmetic sequence

NOTE: The sum of n terms of an arithmetic sequence

[math] S_n = \frac{n}{2} [2a + (n- 1)d][/math]

Where first term ‘a’ and common difference ‘d’ and n = number of terms

Step 2: Setup an equation by substituting all known values in the formula in two cases

EXAMPLE: Case 1: Fist term a = a

Common difference d = 3

n = 50 terms

S_{50}=\frac{50}{2}(2a+(50-1)3)=5200

Step 3: Solve the equation (linear equation) to get the unknown values

NOTE: Solve the linear equations