Question

please help!

The formula for summing an arithmetic progression is S= 0.5n(2a+(n-1)d)
if a = 8, n = 20 and S = 225, find d.

please explain step by step
the answer is d=0.5

Answer 1

s= 0.5n [2a+(n-1)d]

225 = 0.5*20[2*8+(20-1) d]
can u find d now?

Answer 2

do u understand it!!!!!!!!!!!?

Answer 3

just use pemdas

Answer 4

@maryanb

Answer 5

Solution
1 Simplify 20−120−1 to 1919
225=0.5×20(2×8+19d)
225=0.5×20(2×8+19d)

2 Simplify 2×82×8 to 1616
225=0.5×20(16+19d)
225=0.5×20(16+19d)

3 Simplify 0.5×20(16+19d)0.5×20(16+19d) to 10(16+19d)10(16+19d)
225=10(16+19d)
225=10(16+19d)

4 Divide both sides by 1010
22510=16+19d
22510=16+19d

5 Simplify 2251022510 to 452452
452=16+19d
452=16+19d

6 Subtract 1616 from both sides
452−16=19d
452−16=19d

7 Simplify 452−16452−16 to 132132
132=19d
132=19d

8 Divide both sides by 1919
132×19=d
132×19=d

9 Simplify 2×192×19 to 3838
1338=d
1338=d

10 Switch sides
d=13/38

Answer 6

HI!!

Answer 7

you got this or no? explanation above must be from some web site