Question

If S_6=922.32 and r = 4/5, what is the value of a₁?

Answer 1

Answer:

  a₁ = 250

Step-by-step explanation:

Use the given values in the formula for the sum of a geometric series, and solve for the unknown.

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  S₆ = a₁×(1 -r⁶)/(1 -r) . . . . sum of 6 terms of a geometric series

  922.32 = a₁×(1 -(4/5)⁶)/(1 -4/5) = a₁×5×(1 -4096/15625) = a₁×11529/3125

  922.32×3125/11529 = a₁ = 250 . . . . divide by the coefficient of a₁