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A clerk in a clothing department is arranging t-shirts in a display in stacks of equal size.
When he separated the t-shirts into stacks of 4, there was one left over.
When he tried stacks of 5, there was still one left over.
The same was true for stacks of six.
However, he was able to arrange the shirts evenly in stacks of 7. How many t-shirts were in the display that he was arranging?
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The traditional solution for such kind of problems is THIS:
Let N be an unknown number of t-shirts.
Let us take one shirt aside for a moment (mentally) and consider the number N-1.
Then this number is divided by 4, by 5 and by 6 without a remainder.
The smallest such integer is 4*5*3 = 60.
Consider the numbers (a sequence) 60+1=61, 2*60+1=121, 3*60+1=181, 4*60+1=241, 5*60+1=301, . . . and check if these numbers are multiples of 7.
The 301 is (301 = 7*43).
So, your answer is 301.
For similar problem see the lesson
- The number that leaves a remainder 1 when divided by 2, by 3, by 4, by 5 and so on until 9
in this site.