Two cords of rope around a circle wheel of 77 cm radius are to be inserted. so how much rope does it take to roll?
1) 154 cm
2) 968 cm
3) 462 cm
4) 616 cm​

Let the combination be of the form xxx
so, we have 3 digits in our combination, with repetition allowed
so, to type in 1st digit x, we have 10 options i.e. 0 to 9
similarly, to type in 2nd digit, we have 10 options i.e. 0 to 9
again, to type in 3rd digit, we have 10 options i.e. 0 to 9
so, for typing the xxx combination, no. of ways possible will be given by=
(10) x (10) x (10) = 1000

therefore, he can type the combination in 1000 ways.

7: p: : 35: 42

product of mean = product of extreme

p×35=7×42

p=(7×42)/35

p=8.4