Question

There are 5 boxes, each containing 5 cubes of different colours-red, yellow, green, blue and black. I want to draw a different coloured cube from each box. If from the first and the second box, I drew red and green cubes respectively, then what is the maximum number of trials required at the remaining boxes so as to draw different coloured cubes?

• A. 15
• B. 12
• C. 60
• D. 120

Answer 1

The correct option is B

12

Number of trials needed at the 3${}^{rd}$ box to ensure a colour other than green and red is picked is 3
Similarly, number of trials needed at the 4${}^{th}$ box to ensure a new colour is
picked at the maximum=4
And number of trials in the last box to pick a different colour other than
that in the other 4 at a maximum=5.

Total = 3+4+5=12