**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 × 10

^{7}+ 7.2 × 10^{5}and state its answer in standard form.

Solution:Solution:

(a) 0.05079 = 0.0508 (correct to three significant figures)

(b) 5 × 10

^{7}+ 7.2 × 10^{5 }= 500 × 10^{5}+ 7.2 × 10^{5}= (500 + 7.2) × 10

^{5}= 507.2 × 10

^{5}=

**5.072 × 10**^{7}**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: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:Solution:

7 × (2 × 10

^{-2})^{3}– 4.3 × 10^{-5}= 7 × 2^{3}× (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}