Question

Help Mac find the next number in the series.

• A. 1265
• B. 1260
• C. 1270
• D. 1275

Answer 1

The correct option is D 1275

The given series is 7, 20, 65, 270, ___.

We find the following pattern in the series:

7 can be represented as $2\times 5^0+5\times 1=7$

20 can be represented as
$2\times 5^1+5\times 2=2\times 5+10=10+10=20$

65 can be represented as
$2\times 5^2+5\times 3=2\times 25+15=50+15=65$

270 can be represented as
$2\times 5^3+5\times 4=2\times 125+20=250+20=270$

Simlarly, the next number will be
$2\times 5^4+5\times 5=2\times 625+25=1250+25=1275$