Comment Re:Calculators dull minds: throw them out! (Score 1) 113
Without meaning to be a smartarse, there is a shortcut to this (if the root is a whole number less that 100). First, you need to know the cubes of 1-10. ie. 1: 1, 2: 8, 3: 27, 4: 64, 5: 125, 6: 216, 7: 343, 8: 512, 9: 729, 10: 1000. For cubes larger than 1000 look at the last digit of the cube in question. Now look at the cubes of 1-10, and check which cube also finishes in that digit. This gives you the second digit of the two digit cuberoot. Look back at the cube in question, and remove the last 3 digits (normally leaving you with a 3 digit number). Compare this number with the cubes of 1-10 and find the largest one smaller than the 3 digit number left. The cuberoot of this is the first digit. I've explained things horrendously badly, so here's an example for the cuberoot of 175616:
1. Root obviously greater than 10.
2. Look at last digit - it's a 6. The last digit of 6^3=216 is also a 6, so we know our root is somethingty 6.
3. Remove last 3 digits from cube, leaving 175. 175 falls between 5^3 and 6^3, so our first digit is a 5.
4. Answer therefore is 56.
1. Root obviously greater than 10.
2. Look at last digit - it's a 6. The last digit of 6^3=216 is also a 6, so we know our root is somethingty 6.
3. Remove last 3 digits from cube, leaving 175. 175 falls between 5^3 and 6^3, so our first digit is a 5.
4. Answer therefore is 56.
