+11912 You are told that i,331 is a perfect cube.Can you guess without factorisation what is its cube root ? Similarly , guess the cube roots of 4913, 12167,32768.
Pls can you just show and explain me how to do the first one and then i will try all others by myself!im really bad in roots so pls make it easy!
+118608 Mmm lets see. I don't know if you have been given a technique Rosala.
$$\sqrt[3]{4913}$$
What digit cubed ends in 3 .
1^3=1, 2^3=8, 3^3=27, 4^3=64, 5^3 no, 6^3 no, 7^3 yes no 8^3no 9^3=no
I know the number ends in 7 because
7*7=47 9*7=63 No other's will end in 3
10^3=1000 too small
20^3=2^3*10^3=8000 too big
So the number has to be between 10 and 20 and end in 7
So the number has to be 17 
+118608 Mmm lets see. I don't know if you have been given a technique Rosala.
$$\sqrt[3]{4913}$$
What digit cubed ends in 3 .
1^3=1, 2^3=8, 3^3=27, 4^3=64, 5^3 no, 6^3 no, 7^3 yes no 8^3no 9^3=no
I know the number ends in 7 because
7*7=47 9*7=63 No other's will end in 3
10^3=1000 too small
20^3=2^3*10^3=8000 too big
So the number has to be between 10 and 20 and end in 7
So the number has to be 17
