What natural process is responsible for creating sand

Find the next number in the series.

6, 7, 16, 51, 208, ?

What should come in place of? in the given series based on the English alphabetical order?

LPA, PSY, TVW, XYU, ?

Select the correct combination of mathematical signs to sequentially replace the * signs and balance the given equation.

76 * 34 * 23 * 12 * 6 * 21

Select the option that represents the letters which, when sequentially placed from left to right in the blanks below, will complete the letter series.

If digit 2 is interchanged with digit 1, then what will be the value of the following equation?

9 + 6 ÷ 4 × 21 – 5=?

Select the letter-cluster that can replace the (?) in the following series.

DEB, IJG, NOL,   ?,   XVV      

At what time between 2 and 3, the hands of the clock are opposite to each other?