# 2.3.3 Standard Form, PT3 Focus Practice

Question 11:

Solution:
$\begin{array}{l}0.000064-3.5×{10}^{-6}\\ =6.4×{10}^{-5}-3.5×{10}^{-6}\\ =6.4×{10}^{-5}-0.35×{10}^{-5}\\ =\left(6.4-0.35\right)×{10}^{-5}\\ =6.05×{10}^{-5}\end{array}$

Question 12:

Solution:

Question 13:
Find the product of 0.1985 and 0.5.
Round off the answer correct to two significant figures.

Solution:
0.1985 × 0.5
= 0.09925
= 0.10 (two significant figures)

Question 14:
The area of a rectangular public parking area is 7.2 km2 . Its width is 2400 m. The length, in m, of the parking area is

Solution:

Question 15:
It is given that 30 solid metal cylinders each with a radius of 70 cm and a height of 300 cm, are melted to make 40 identical solid spheres.
Find the volume, in cm3 , of each solid sphere.

Solution: