There are 4 letters and 4 envelopes. In how many ways can wrong choices be made?
1). 43
2). 4! – 1
3). 16
4). 44 – 1
Number of ways in which letters can be placed in envelopes = 4!
Number of ways of putting all the four letters in correct envelopes = 1
∴ Number of ways in which wrong choice can be made = 4! - 11. Which of the following does not belong to the group?
2. The variance of a set of data is 121. Then the standard deviation of the data is:
5. If a particle moves with a constant speed, the distance-time graph is ________.
7. If tan A + sin A = p and tan A – sin A = q, then
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