Kiran Raj, son of Dhoni is aged 3 years. Dhoni and his wife Amarinder admitted him in a play school. Yuvaraj, 24 year old instructor at the play school taught Kiran Raj the game of construction of plastic blocks of same size but in different colours. Children were expected to construct the blocks one above the other and allow it to stay at the end of every minute. Yuvaraj was enjoying the activity in a funny way. He was constructing 9 blocks in the first minutes and in the following minute he was removing 4 blocks. Surprisingly Kiran Raj was repeating the same feat for 31 minutes. At the end of 31st minute how many blocks would he have constructed?

a) 80 b) 75 c) 83 d) 84

• d) 84
  
  Kiran Raj constructs 9 blocks in the first minute and removes 4 blocks in the second minute. So at the end of 2nd minute he would have constructed 5 blocks.
  Assuming he repeats this process till 30 minutes (15 x2) – he would have constructed 75 blocks (i.e.15 x 5 ). So in the 31st minute he will construct 9 blocks and at the end of 31st minute he would have constructed 75 + 9 = 84 blocks.
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