Question

B. Round off each of the followingquantities to two significant figures :a. 25.55 mLb. 0.00254 mc. 1.491 x 105 mg d. 199 g

Answer 1

Answer:

a) $2.5\times 10^{1}$

b) $2.5\times 10^{-3}$

c) $1.4\times 10^{5}$

d) $1.9\times 10^{2}$

Explanation:

Significant figures : The figures in a number which express the value -the magnitude of a quantity to a specific degree of accuracy is known as significant digits.

Scientific notation is defined as the representation of expressing the numbers that are too big or too small and are represented in the decimal form with one digit before the decimal point times 10 raise to the power.

For example : 5000 is written as $5.0\times 10^3$

a) 25.55 ml in two significant digits is $2.5\times 10^{1}$

b) 0.00254  in two significant digits is $2.5\times 10^{-3}$

c) $1.491\times 10^{5}$ mg in two significant digits is  $1.4\times 10^{5}$

d) 199 g in two significant digits is  $1.9\times 10^{2}$

Answer 2

(a) 25.55 mL = 2.6 × 10¹ mL

(b) 0.00254 m = 0.0025 m

(c) 1.491 × 10⁵ mg = 1.5 × 10⁵ mg

(d) 199 g = 2.0 × 10² g

Explanation :

Significant figures : The figures in a number which express the value -the magnitude of a quantity to a specific degree of accuracy is known as significant digits.

Scientific notation is defined as the representation of expressing the numbers that are too big or too small and are represented in the decimal form with one digit before the decimal point times 10 raise to the power.

The following rules are used to round off a number to the required number of significant figures:

• If the rightmost digit to be removed is more than 5, the preceding number is increased by one.
• If the rightmost digit to be removed is less than 5, the preceding number is not changed.
• If the rightmost digit to be removed is 5, then the preceding number is not changed if it is an even number but it is increased by one if it is an odd number.
• The same procedure is follow for decimal values.

(a) 25.55 mL = 2.6 × 10¹ mL

(b) 0.00254 m = 0.0025 m

(c) 1.491 × 10⁵ mg = 1.5 × 10⁵ mg

(d) 199 g = 2.0 × 10² g

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