Question

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Answer 1

what formula are you using?

Answer 2

i divide it into three groups

Answer 3

that will not work ...

Answer 4

you can't express a cube as sum of two cubes

Answer 5

cube root (1000100) = cuberoot(1000000) + cuberoot(1000) = 100 + 10 = 110

110^3 = 1331000 ... you should know that you can't apply this one

Answer 6

@msingh
your estimation method works, bot only if you split it into 2 groups, not 3:

solution:
1 953 125
Make TWO groups:
first group = 125
the no. ends up with 5. therefore, if the digit 5 is at the end of a perfect cube no, then its cube root is taken 5 as the unit place.
Now,
second group = 1953
12*12*12=1728
13*13*13= 2197
so
1278<1953<2197^
12^3 <1953<13^3
therefore, 12 is taken at the ten's place.
125

so as you can tell, not really a feasible method as while some might know the cube of 1-10 of the top of their head, very few people learn the double digit cubes

Answer 7

not that these are estimation methods perse

the square root by hand method follows a: x^2 + 2xy + y^2

the cuberoot by hand method: x^3 +3x^2y+3xy^2 + y^3 which is alot more difficult to play with.