Determine which of these is larger:
29√14 + 4√15 or, 124
*** For an extra challenge, solve this problem using only pen and paper.
(In reply to
re: the hard way....slightly softened by Ady TZIDON)
It is not "as Ady seems to know"-
I've mentioned in the text:
-easy to check that 14.5^2=210.25
To square any number ending by 5, say 10n+5 you mentaly
multiply n by n+1 and append the result by 25,
e.g. to evaluate 145^2 ==> 14*15=210,
so the result is 21025. In our case 210.25 .
Since you like proofs to a rule of thumb:
(10n+5)^2=100n^2+100n+25 =100n*(n+1)+25
Few examples: (no pen & paper)
65==>4225, 115==>13225, 1005==>1010025.
Dixi.
re(2): the hard way....slightly softened
