I got this activity from Mental Math Workout by Michael Lobosco
142857 is a cyclic number.
1/7 = 0.142857142857
Have a student roll a dice. Have the class multiply 142857 by the number .
You can write the answer on the board. For example if a 4 is rolled you just multiply 4 and 7 .
The final digit in the answer is 8 so the complete answer is
To add a little twist to this I took the activity from the Lobosco book. I held up an envelope with the answer inside. I had prepared a loop of paper and placed so that the flap of the envelope separates 142 and 857. Using the example above I would cut the loop between 8 and 5 to give the answer
The last class I did this with had difficulty. The number we rolled was 6 and only 4 students in the class could multiply 142857 by 6 so the majority were not impressed when I revealed the answer as 857 142 ,
Later in the day we took out calculators and looked at turning fractions into decimal numbers
1/2 = 0.5
1/3 = 0.333
1/4 = 0.25
We discussed the pattern that we saw in the decimal answers for the sevenths.
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