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Prime Time > Fun with Numbers

Fun with Numbers

Special numbers

There are four numbers in this box.

Which number looks special to you? Why do you say so?

916
2543

Look at what Guna's classmates have to share:

Karnawati says, "9 is special because it is a -digit number whereas all the other numbers are -digit numbers".

Gurupreet says, "9 is special because it is the only number that is a of 3".

Murugan says, "16 is special because it is the only even number and also the only of 4".

Gopika says, "25 is special as it is the only of 5".

Yadnyikee says, "43 is special because it is the only number".

Radha says, "43 is special because it is the only number that a square".

Below are some boxes with four numbers in each box. Within each box try to say how each number is special compared to the rest. Share with your classmates and find out who else gave the same reasons as you did. Did anyone give different reasons that may not have occurred to you?

Box 1:

57
1235

Answer:

Instruction

5 is special because it is the prime number in the box
7 is special because it is the prime number in the box
12 is special because it is the only number
35 is special because it is the number and the only multiple of 5

Box 2:

38
1124

Answer:

Instruction

3 is special because it is the number and prime
8 is special because it is the only perfect
11 is special because it is the largest number
24 is special because it is the number and has the most factors

Box 3:

273
12331

Answer:

Instruction

27 is special because it is the only perfect cube 3
3 is special because it is the number and has digit
123 is special because it is the largest number and has digits
31 is special because it is the only number

Box 4:

1727
4465

Answer:

Instruction

17 is special because it is the only number
27 is special because it is the only perfect cube 3
4 is special because it is the only number
65 is special because it is the number and ends in 5

A prime puzzle

The figure on the left shows the puzzle. The figure on the right shows the solution of the puzzle. Think what the rules can be to solve the puzzle.

Rules

Fill the grid with prime numbers only so that the product of each row is the number to the right of the row and the product of each column is the number below the column.