a circle has a radius of 7 cm. what is its area? (use π≈3.14) * 49 cm² 100 cm² 38.5 cm² 153.86 cm² which of…

Explanation:

Step1: Recall area - formula for circle

The formula for the area of a circle is $A = \pi r^{2}$, where $r$ is the radius.

Step2: Substitute the given values

Given $r = 7$ cm and $\pi=3.14$, we substitute into the formula: $A=3.14\times7^{2}$.

Step3: Calculate the result

First, $7^{2}=49$, then $A = 3.14\times49=153.86$ $cm^{2}$.

For the prime - number question:

Step1: Recall the definition of prime number

A prime number is a positive integer greater than 1 that has exactly two distinct positive divisors: 1 and itself.

Step2: Analyze each option

• For 15: $15=3\times5$, so it has more than two positive divisors.
• For 17: Its positive divisors are 1 and 17 only.
• For 27: $27 = 3\times9$, so it has more than two positive divisors.
• For 21: $21=3\times7$, so it has more than two positive divisors.

Answer:

1. D. $153.86$ $cm^{2}$
2. B. 17