Day Two Try these. 1


Jenny thought of a number. She added 2 to it and squared it. She ended up with 81. Work backwards to work out the number that she started with.


Answer: 2


Marks:


Jack multiplied a number by 16. The square root of Jack’s new number was 8. What was the number Jack thought about at the start?


Answer: 3


Marks:


? /2 ? /2


I am a composite number. I have four factors, all of which are odd. I am an odd number too. The sum of my factors is 24. What number am I?


Answer: Marks: 4 Using a calculator, try the following activity with five prime numbers no lower than 5:


Step 1 − Square your prime number (i.e. multiply your prime number by itself). Step 2 − Take away 1.


Once you have all five answers, look for a common link between them. Share your thoughts with your classmates.


Top tip: Work systematically.


Top tip: Use trial and improvement.


/2


Answer: Super Sleuth investigates


Use a calculator for this activity. 220 and 284 are amicable numbers. Follow these steps: Step 1 − F220 = ( ,


, , , , , , , , Step 4 Add the factors of 284. Don’t include 284.


What did you notice in this activity? Discuss your thoughts with a partner and share your definition of amicable numbers with your class.


Today’s Marks: /8 89 ,


Step 2 − Add the factors of 220. Don’t include 220. Step 3 − F284 = (


, 284) , , , , , 220)


Marks:


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Week 21 | Number Theory


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