Questions

The owner first lost Rs. 100 in cash, but after the thief bought Rs. 60 goods, he get back that Rs. 100 but he lost Rs. 60 value of goods and Rs. 40 in change.

So, a total of 60 + 40 = Rs. 100 the owner lose.

Ecology is the branch of science which deals with the study of Ecosystem (relation between the Organisms and their Environment.)

VOIP is an acronym for Voice Over Internet Protocol, or in more common terms phone service over the Internet.

Voice over Internet Protocol is a category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls by sending voice data in packets using IP rather than by traditional circuit transmissions of the PSTN.

Here in the given options, Skype is the only voice service that enables us to talk over internet.

At least one black can be chosen in two ways from each box:
Now, probability of choosing at least one black ball from first box 

= 1/2 × [ (2C1× 2C1)/4C2 + 2C2/ 4C2 ]= 5/12

Probability of choosing at least one black ball from 2nd box
= 1/2 × [(4C1×12C1)/16C2 + 4C2/ 16C2] = 9/40

Final probability

= 5/12 + 9/40 = (50 + 27)/120 = 77/120