MCQ
If three positive numbers are inserted between 4 and 512 such that the resulting sequence is a G.P., which of the following is not among the numbers inserted?
- A256
- B16
- C64
- D128
Solution:
Let G.P. be 4, G1, G2, G3, 512.
⇒ a = 4 and a5 = a × r4 = 512 × 4 × r4 = 512 ⇒ r4
$=\frac{512}{4}=128\Rightarrow\text{r=4.}$
G1 = a2 = a × r = 4 × 4 = 16.
G2 = G1 × r = 16 × 4 = 64.
G3 = G2 × r = 64 × 4 = 256.
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