# Questions tagged [formation-of-numbers]

For puzzles about forming numbers using other numbers and mathematical operations.

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951 views

### Make 12 with 1, 5, 19, 10

How can you make the number 12 with just the numbers 1,5,19,10? You can only use each number once, and can only use subtraction addition multiplication and division.
395 views

### Arrange (+,-,x,/) into the upsilon grid

Put operators $(+,-,×,/)$ into the squares. Each operator must appears exactly 3 times to make the operations correct. C is a constant. No BODMA rules ((×) and (/) is NOT HIGHER than (+) and (−)), do ...
352 views

### Arrange numbers 1 to 9 into the upsilon grid

Arrange numbers 1 to 9 into the octagon, so the operation is correct. C is a constant. Do the math operation in sequence, ($×$) and ($/$) is NOT HIGHER than ($+$) and ($-$).
371 views

### The pre-alpha calculator

You are given a rudimentary prototype of a calculator with only the following keys: 0 1 2 3 4 5 6 7 8 9 + - × ÷ = The display has place for 10 digits and is initially showing ...
173 views

### Robbers - Make 24 [closed]

The make-24 puzzle is an oldie, but a very fun one at that. Given four different numbers, produce—through a sequence of operations upon only those four numbers—the number twenty-four. For example, ...
301 views

### Coppers - Make 24 [closed]

The make-24 puzzle is an oldie, but a very fun one at that. Given four different numbers, produce—through a sequence of operations upon only those four numbers—the number twenty-four. For example, ...
862 views

2k views

### Finding the largest 7-digit number

Find the largest 7-digit number without its digits repeating, such that the number is divisible by all of its digits I found some constraints: • 0,4 and 5 cannot be included • The number found should ...
270 views

### Find a Strobogrammatic number, so if we square it, the result is a pandigit number

Find a Strobogrammatic number, so if we square it, the result is a pandigit number. Note : A Strobogrammatic number is a number when typed on a calculator, and the calculator is spun 180 degrees, ...
508 views

### Find the rule : triplet number into Positive Integer

These are triplets of numbers into positive integers: ...