When they danced as couples there was one person left over.
When they danced in threes one person was left over.
When they danced in fours one person was left over.
When they danced in fives one person was left over.
Topics: Starter  LCM  Number
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Previous Day  This starter is for 28 January  Next Day
Students could use a spreadsheet to create a list of possible numbers of people at the dance. Columns could be set up to show the remainder after dividing by 2 or 3 etc. The MOD function could be used for this:
Eg =MOD(A7,4) shows the remainder when the number in cell A7 is divided by 4.
What if the problem above was changed?
What if the group sizes were 3,5,7 and 8?
This Starter is a simple problem which can be solved by using the Chinese remainder theorem first published in the 3rd to 5th centuries by the Chinese mathematician Sun Tzu. In its basic form, the Chinese remainder theorem will determine a number n that, when divided by some given divisors, leaves given remainders.
What is the lowest number that
when divided by 3 leaves a remainder of 2,
when divided by 5 leaves a remainder of 3,
and when divided by 7 leaves a remainder of 2?
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