yuctoborian : a math shortcut for squaring numbers that end in 5

Squares of halves

1.52 = ( 1 x 2 ) + 0.25 = 2.25

2.52 = ( 2 x 3 ) + 0.25 = 6.25

3.52 = ( 3 x 4 ) + 0.25 = 12.25

4.52 = ( 4 x 5 ) + 0.25 = 20.25

1.52 = ( 1 x 2 ) + 0.25 = 2.25

2.52 = ( 2 x 3 ) + 0.25 = 6.25

3.52 = ( 3 x 4 ) + 0.25 = 12.25

4.52 = ( 4 x 5 ) + 0.25 = 20.25

1.52 = ( 1 x 2 ) + 0.25 = 2.25

2.52 = ( 2 x 3 ) + 0.25 = 6.25

3.52 = ( 3 x 4 ) + 0.25 = 12.25

4.52 = ( 4 x 5 ) + 0.25 = 20.25

1.52 = ( 1 x 2 ) + 0.25 = 2.25

2.52 = ( 2 x 3 ) + 0.25 = 6.25

3.52 = ( 3 x 4 ) + 0.25 = 12.25

4.52 = ( 4 x 5 ) + 0.25 = 20.25

1.52 = ( 1 x 2 ) + 0.25 = 2.25

2.52 = ( 2 x 3 ) + 0.25 = 6.25

3.52 = ( 3 x 4 ) + 0.25 = 12.25

4.52 = ( 4 x 5 ) + 0.25 = 20.25

In other words, multiply the whole numbers above and below the half, then add 0.25.

1.52 = ( 1 x 2 ) + 0.25 = 2.25

2.52 = ( 2 x 3 ) + 0.25 = 6.25

3.52 = ( 3 x 4 ) + 0.25 = 12.25

4.52 = ( 4 x 5 ) + 0.25 = 20.25

In other words,

multiply the whole numbers above and below the half,

1.52 = ( 1 x 2 ) + 0.25 = 2.25

2.52 = ( 2 x 3 ) + 0.25 = 6.25

3.52 = ( 3 x 4 ) + 0.25 = 12.25

4.52 = ( 4 x 5 ) + 0.25 = 20.25

In other words,

multiply the whole numbers above and below the half,

Then add 0.25

Squares of whole numbers ending in 5

152 = 1x2 then attach 25 = 225

252 = 2 x 3 then attach 25 = 625

752 = 7 x 8 then attach 25 = 5625

8052 = 80 x 81 then attach 25 = 648025

152 = 1x2 then attach 25 = 225

252 = 2 x 3 then attach 25 = 625

752 = 7 x 8 then attach 25 = 5625

8052 = 80 x 81 then attach 25 = 648025

152 = 1x2 then attach 25 = 225

252 = 2 x 3 then attach 25 = 625

752 = 7 x 8 then attach 25 = 5625

8052 = 80 x 81 then attach 25 = 648025

152 = 1x2 then attach 25 = 225

252 = 2 x 3 then attach 25 = 625

752 = 7 x 8 then attach 25 = 5625

8052 = 80 x 81 then attach 25 = 648025

Squares of decimal numbers ending in 5

0.752 = 7 x 8, then attach 25 = 5625

0.752 = 7 x 8, then attach 25 = 5625

(But where does the decimal point go?)

0.752 = 7 x 8, then attach 25 = 5625

(But where does the decimal point go?)

The number is ‘three-quarters of three-quarters.’

That has to be close to ½.

0.752 = 7 x 8, then attach 25 = 5625

(But where does the decimal point go?)

The number is ‘three-quarters of three-quarters.’

That has to be close to ½.

(But where does the decimal point go?)

0.752 = 7 x 8, then attach 25 = 0.5625

1.052 = 10 x 11 then attach 25 = 11025

0.752 = 7 x 8, then attach 25 = 0.5625

1.052 = 10 x 11 then attach 25 = 11025

The answer has to be slightly larger than 1.

0.752 = 7 x 8, then attach 25 = 0.5625

1.052 = 10 x 11 then attach 25 = 1.1025

0.752 = 7 x 8, then attach 25 = 0.5625

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