If a is an integer, which of the 
following could be a4 ?
A. 1.6 X 10^11
B. 1.6 X 10^12
C. 1.6 X 10^13 
D. 1.6 X 10^14
E. 1.6 X 10^15



Answer :

So to work this out we need to find the 4th root of each of those and pick the one that gives an integer.

A: [tex] \sqrt[4]{1.6*10^1^1} = 632.455...[/tex] This is a decimal therefore not an integer.

B: [tex] \sqrt[4]{1.6*10^1^2} =1124.682...[/tex] Again a decimal, therefore not an integer.

C: [tex] \sqrt[4]{1.6*10^1^3} =2000[/tex] This is a whole number, so it is an integer.

D: [tex] \sqrt[4]{1.6*10^1^4} =3556.558...[/tex] Decimal, therefore not an integer

E: [tex] \sqrt[4]{1.6*10^1^5} =6324.555...[/tex] Again a decimal, not an integer.

The only one that gives an integer when put to the 4th root is C, therefore:

[tex]1.6*10^1^3[/tex] could be A^4, as the 4th root of it is an integer.