2 73 – 2 72 – 2 71 is the same as

2 71 — 2 73 – 2 72 – 2 71 = 2 71 (2 2 – 2 1 - 1) = 2 71 (4 - 2 - 1) = 2 71 (1) = 2 71 Hence, option (c).

CAT 1991 — QA Question 20

IndicesEasy

Passage / Data

Use the following information:

Prakash has to decide whether or not to test a batch of 1000 widgets before sending them to the buyer. In case he decides to test, he has two options: (a) Use test I ; (b) Use test II. Test I cost Rs. 2 per widget. However, the test is not perfect. It sends 20% of the bad ones to the buyer as good. Test II costs Rs. 3 per widget. It brings out all the bad ones. A defective widget identified before sending can be corrected at a cost of Rs. 25 per widget. All defective widgets are identified at the buyer’s end and penalty of Rs. 50 per defective widget has to be paid by Prakash.

2⁷³ – 2⁷² – 2⁷¹ is the same as

Answer & solution

A
2⁶⁹
B
2⁷⁰
2⁷¹
D
2⁷²

Solution

2⁷³ – 2⁷² – 2⁷¹ = 2⁷¹(2² – 2¹ - 1) = 2⁷¹(4 - 2 - 1) = 2⁷¹(1) = 2⁷¹

Hence, option (c).