A drink coaster in the shape of a circle has
an area of 19.63 square inches. Find the
diameter of the coaster.

The diameter of the coaster is 5 cm.

Step-by-step explanation:

Given,

The area of the circle = 19.63 sq inch

To find the diameter, we need to find the radius

Formula

The area of a circle with radius(r) = π sq cm

According to the problem,

π  = 19.63

or, =

= 6.2459

or, r = = 2.499 (approx)

= 2.5 cm

Hence the diameter of the circle  = 2 × 2.5 cm = 5 cm

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.