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what is 25 squared solved out just in your head?

 Mar 26, 2015

Best Answer 

 #2
avatar+99352 
+5

I could do that in my head Chris but then I am a show off.  LOL

 

Here is another easier way and it works for all numbers ending in 5

 

25^2=2^2+2 then add 25 = 625

75^2 = 7^2+7 then add 25 = 5625

35^2=3^3+3 then add 25 = 1225

105^2=10^2+10 then add 25 = 11025

etc.

That is really easy to do in your head :)

 Mar 26, 2015
 #1
avatar+98173 
+5

I always think of things like that in this way :

(20 + 5) (20 + 5)

I see that multiplying the first two terms gives me 400

Then, I have 5 x 20,  twice  = 200

Finally, the last two terms multiplied together = 25

So..adding the results, we have......400 + 200 + 25 = 625

{However....since I just did this on "paper".....I guess it wasn't done in my head after all....!!! }

 

  

 Mar 26, 2015
 #2
avatar+99352 
+5
Best Answer

I could do that in my head Chris but then I am a show off.  LOL

 

Here is another easier way and it works for all numbers ending in 5

 

25^2=2^2+2 then add 25 = 625

75^2 = 7^2+7 then add 25 = 5625

35^2=3^3+3 then add 25 = 1225

105^2=10^2+10 then add 25 = 11025

etc.

That is really easy to do in your head :)

Melody Mar 26, 2015

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