Question

The number of significant figures in 0.06900 is
(a) 5
(b) 4
(c) 2
(d) 3

Answer 1

Hint: We know that numbers are often rounded to avoid reporting insignificant figures. If the scale of the vendor only gives the nearest number and if it gives a reading of 11.225kg which has 5 significant figures. Many times numbers are rounded up for simplicity and not for the sake of precision. Thus, by using these laws we can convert the figures into significant numbers.

Complete step by step answer:
Before solving the problem, we will understand a few rules of significant figures. So, the rules are as follows:

(i)First rule is that all non-zero digits are considered as significant: 1, 2, 3, 4…….
(ii)Then the second rule is Zeros between non-zero digits are also considered as significant: 102, 200005, 25020…..
(iii)Now, the third rule can be given as: Leading zeros are never significant: 0.02, 001.887, 0.000515.
(iv)Fourth and most significant rule is that in a number with or without a decimal point, trailing zeros which are on the right of the last non-zero digit are significant if they are justified by the precision of their derivation: 252,0000; 5.02121000; 6.900; 42.697800

Now, on the basis of the rules, it can be said that our number 0.06900, have 4 significant figures as zeroes before the non-zero numbers are considered as insignificant.
Thus, option (b) is the correct answer.

Note: Significant numbers also depend on the precision required in the value. For example, if the value is 123.4560000, and if it is asked to write the answer up till 5 decimal points then we have to consider 5 digits from decimal point i.e. 4,5,6,0 and 0. In this case significant numbers will be total 8 i.e. 1,2,3,4,5,6,0 and 0. Now, if it is asked to find the answer up to 1 decimal only then our answer will be 123.4 and significant figures will be all four digits. In this case rest of digits are of no use as per the requirement. So, this is the most important thing to be kept in mind for such types of problems.