4) Rohit while going to a stationary shop decided to buy a certain number of pens and pencils. On reaching the shop, he bought 50% more pens and 25% less pencils than what he decided, but the overall number of items remains same. By what percent will the number of items increase if he buys 16.66% more pens and .66.66% more pencils than what he decided?

answer is the 50%
25% percent less equals to the 50% more which means initially assumed number of pens to the number of pencils is 1:2
now assume any numbers increase them as said in the question and you will get the answer.

Pre decides no of pens and pencils: p+Q
No he bought: 1.5p + 0.75q
Given both are equal, so 0.5p = 0.25q. P/q= 1/2. Assume the p = 100, q = 200 . Then just add 16.66 and 66.66 you will get 450. Which is 150 more than the initial assumed 300 (100+200). So the answer is 50%

1/6=16.66%. This is the answer.