निम्नलिखित प्रश्नों

A sum of money doubles itself at the compound interest x in 10 years. In how many years it will be four times at the same compound interest? 

In the following series, only one letter-cluster is incorrect. Select the incorrect letter-cluster.

YCG IMQ SVZ CGK MQU

Which letter-cluster will replace the question mark (?) to complete the given series?

MKPN, LMOP, ?, JQMT, ISLV

Select the figure which satisfies the same conditions of placement of the dots as in Figure-X.

If 'A' stands for '÷ ', 'B' stands for '×', 'C' stands for + and 'D' stands for '–', what will come in place of the question

Select the combination of letters that when sequentially placed in the blanks of the given series will complete the series.