# 1.3 Standard Form, SPM Practice (Paper 1)

1.3 Standard Form, SPM Practice (Paper 1)
Question 6:
(a)  Round off 0.05079 correct to three significant figures.
(b)  Find the value of 5 × 107 + 7.2 × 105 and state its answer in standard form.

Solution:
(a)  0.05079 = 0.0508 (correct to three significant figures)
(b)  5 × 107 + 7.2 × 105 = 500 × 105 + 7.2 × 105
= (500 + 7.2) × 105
= 507.2 × 105
= 5.072 × 107

Question 7:
(a)  Calculate the value of 70.2 – 3.22 × 8.4 and round off its answer correct to two significant figures.
(b)  Express $\frac{840}{0.000021}$  as a number in standard form.

Solution:
(a)  70.2 – 3.22 × 8.4 = 70.2 – 27.048
= 43.152

(b)

Question 8:
Calculate the value of 7 × (2 × 10-2)3 – 4.3 × 10-5 and state its answer in standard form.

Solution:
7 × (2 × 10-2)3 – 4.3 × 10-5 = 7 × 23 × (10-2)3 – 4.3 × 10-5
= 56 × 10-6 – 4.3 × 10-5
= 5.6 × 10-5 – 4.3 × 10-5
= 1.3 × 10-5