Aptitude Discussion

Q. |
How many factors of $2^4 × 5^3 × 7^4$ are odd numbers? |

✔ A. |
$20$ |

✖ B. |
$24$ |

✖ C. |
$30$ |

✖ D. |
$36$ |

**Solution:**

Option(**A**) is correct

Any factor of this number should be of the form $2^a × 3^b × 5^c$.

For the factor to be an odd number, $a$ should be $0$.

$b$ can take values $0,1, 2,3$ and $c$ can take values $0, 1, 2,3, 4.$

Total number of odd factors,

$= 4 × 5$

$= \textbf{20}$

**VEERARAGAVAN C S**

*()
*

there is a mistake in the first line.

it should be $2^a \times 5^b \times 7^c$. Since none of the factors of the given number is a multiple of 3