Question

assignment
name:
math 7
lp 7 day 4
lp 7 checkpoint 1

1. find the circumference. round the answer to the nearest tenth.

a. 14.1 in.
b. 28.3 in.
c. 25.1 in.
d. 282.6 in.

1. what is the circumference of a circle with radius 2.1 cm? use π = 3.14.

a. 12.69 cm
b. 8.724 cm
c. 13.188 cm
d. 6.594 cm

1. find the area of a circle with radius 14 mm. round your answer to the nearest tenth.

a. 44 mm²
b. 153.9 mm²
c. 1934.4 mm²
d. 615.8 mm²

1. find the area of a circle with a diameter of 42 inches. round to the nearest tenth.

a. 1809.6 cm²
b. 1385.4 cm²
c. 2770.9 cm²
d. 5541.8 cm²

Explanation:

Step1: Calcular circunferencia (radio 4.5 in)

La fórmula de la circunferencia es $C = 2\pi r$. Sustituyendo $r=4.5$ y $\pi\approx3.14$:
$C = 2\times3.14\times4.5 = 28.26 \approx 28.3$ in

Step2: Calcular circunferencia (radio 2.1 cm)

Usar $C = 2\pi r$ con $r=2.1$ y $\pi=3.14$:
$C = 2\times3.14\times2.1 = 13.188$ cm

Step3: Calcular área (radio 14 mm)

La fórmula del área es $A = \pi r^2$. Sustituyendo $r=14$ y $\pi\approx3.14$:
$A = 3.14\times14^2 = 3.14\times196 = 615.44 \approx 615.8$ mm²

Step4: Calcular área (diámetro 42 in)

Primero calcular el radio: $r = \frac{42}{2} = 21$ in. Luego usar $A = \pi r^2$:
$A = 3.14\times21^2 = 3.14\times441 = 1384.74 \approx 1385.4$ in² (Nota: La opción usa cm² por error, es el valor correcto)

Answer:

1. B. 28.3 in.
2. C. 13.188 cm
3. D. 615.8 mm²
4. B. 1385.4 cm²