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Manager
Joined: 05 Mar 2011
Posts: 160
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How many of the three-digit numbers are divisible by 7?
105
106
127
128
142
Approach One: Divide all of the three-digit numbers (Don't forget to add 1 to get the number of all the 3-digit numbers) by 7, which is 128.57, and then round it off to 128.
Approach Two: Find the first and the last multiples of 7 WITHIN the range (which is between 105 and 994). Find the positive difference, divide by 7, and add 1:
994-105/7+1=128
I hv a qs about this approach 1 -I followed the mgamt approach which took me a lot longer to solve which is the 2nd approach mentioned in this prob
but when I tested approach 1 for anther prob of the similar type i got the ans wrong
how many nos betw 94 and 302 are / by 3
302-94+1=209
209/3=69.66777 which rounded of is 70 not 69
if u use mgmat approach
the ans is 69
M i missing something?
300-96/3+1=69
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Senior Manager
Joined: 18 Sep 2009
Posts: 373
Followers: 3
Kudos [?]:
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how many nos betw 94 and 302 are / by 3
302-94+1=209
209/3=69.66777 which rounded of is 70 not 69
the value is 69.66. the value after decimal is more than 5 so we need to round up to 70.
If the value is 69.2 (lessthan 5 like 1,2,3,4 it must be 69 )
If the value is 69.66(more than 5 like 5,6,7,8,9 it must be 70)
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