Weekly Logic Puzzle August 18 2015, 0 Comments

math resources for special education students

Last Week's Puzzle 

Seven people meet at a party. Each person shakes hands once with every other person at the party. How many handshakes take place?

Answer: 

21 handshakes. Two ways to figure this out are:

Take one person in the group. That person will shake the hands of the other six. Take a second person. That person will shake the hands of the 5 remaining people. Continue until just two people are left and have one handshake. The number of handshakes is 6+5+4+3+2+1 = 21.

It can also be looked at as a combination problem. nCr = n! / (r! * (n - r)!) Since 7 people with combination of 2 required for handshake = 7C2  

= 7! / (2! * (7 - 2)!)

= 7! / (2! * 5!)

= 7 * 6 * 5! / (2! * 5!)

= 7 * 6 / 2

= 21 

This Week's Puzzle

The sum of three consecutive numbers is 345. Can you figure out the three numbers?

A new puzzle is posted weekly. Post your guesses below and check back next week to find out the answer!

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Luminous Learning math worksheets with number lines and graph paper for special education students