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The value of the Euler Totient function $\phi (n)$ at 400 is : |
96 60 120 160 |
160 |
The correct answer is Option (4) → 160 $400=2^4×5^2$ $\phi(n)=n\left(1-\frac{1}{p_1}\right)\left(1-\frac{1}{p_2}\right)....\left(1-\frac{1}{p_n}\right)$ $\phi(400)=400×\left(1-\frac{1}{2}\right)\left(1-\frac{1}{5}\right)$ $=400×\frac{1}{2}×\frac{4}{5}=160$ |
