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how to make quick calculations


savita

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Q 1. If it is 6:27 in the evening on a certain day, what time in the morning was it exactly 2,880,717 minutes earlier ? (assume standard time in one locations.

a. 6.22

b. 6.24

c. 6:27

d: 6.30

e. 6.32

 

 

Q2. If n is an integer which of the following CANNOT be a factor of 3n+4

a. 4

b. 5

c. 6

d. 7

e. 8

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2. ©

 

3.8 + 4 = 28 , 4 and 7 are factors so that rules out A and D

3.12+4 = 40 , 5 and 8 are factors, so that rules out B and E

 

Answer is C

 

or 3n + 4 means a number like 40 = 3.12+4 this will always leave a remainder of 1

hence not divisible by 3

 

hence not divisible by 6 regardless of whether divisible by 2 or not. (i.e. whether n is even or not)

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I guess, for this problem one need not even do calculation by just looking answer choices. If it is 6.27, then 7 minutes earlier or 17 minutes earlier or 717 minutes earlier the final time would be some number that ends with digit 0. so the obvious answer choice is D
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