+0  
 
0
209
1
avatar

How do I add numbers 119 through 220 quickly without a calculator?

Guest Aug 21, 2017
edited by Guest  Aug 21, 2017
 #1
avatar+86915 
+1

 

Note that we have

 

119 + 120 + 121 +  ..... +  218 + 219 + 220

 

We can rearrange this as

 

(119 + 220 )   + (120 + 219)  + ( 121 + 218) +  ........

 

Note that each pair sums to 339

 

And we have  [ 220 - 119 + 1] / 2  = 51 pairs

 

So....51 (339)  = 17,289

 

 

cool cool cool

CPhill  Aug 21, 2017

2 Online Users

New Privacy Policy

We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive information about your use of our website.
For more information: our cookie policy and privacy policy.