Video: Mentally Calculating 10 More Than a Given Two-Digit Number

Which is the missing piece from this part of the hundred square?

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Video Transcript

What is the missing piece from this part of the hundred square?

The shaded square is the missing piece from the hundred square. This is the number we need to find. The number at the centre of the puzzle is 43.

The number which comes before a given number on a hundred square or to the left of a given number on the hundred square is always one less. And the number after or to the right of a given number on a hundred square is always one more.

The number above a given number is always 10 less, and the number which comes below a given number on a hundred square, which is our missing number, is always 10 more. So our missing number is 10 more than 43.

When we add 10 to a number, the ones digit stays the same and the tens digit increases by one. 43 and 10 more equals 53. The missing piece from the hundred square is number 53.

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