Question 355704: How many 7 digit phone numbers are avaliable if the first three digitd sre either 345, 286 or 329. Could you please explain using 7!, 3! etc
Answer by sudhanshu_kmr(1152)   (Show Source):
You can put this solution on YOUR website!
Here we have to create 7 digit phone number.
when first three digit is 345, we can choose any digit 0-9 for each place.
for example- 3450000, 3450005, 3452010 and so on.
For each place, no. can be choose by 10C1 = 10
so, total no. of ways = 10 * 10 * 10 * 10 = 10000
similarly, for 286 and 329 there are 10000 possible no. can be formed.
total no. of 7 digit number if the first three digitd sre either 345, 286 or
329. = 10000 * 3 = 30000
Sometimes there may be typing mistake in solution of a problem, so please ignore it. Understand the concept and try to solve the problem yourself. If there is problem related to concept, contact at
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Best of luck.......
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