I think it’s 3 because it’s just how I think it is I’m probably not correct but I think it’s 3
Since the precision of the voltmeter is <span>±0.005 V, the effective value range for the first measurement is 9.000 V to 9.010 V, for the second it is 9.001 V to 9.010 V, the third 9.013 V to 9.023 V and the fourth 9.021 V to 9.030 V. From all of these measurements the only one which the accepted value falls within the range is measurement 3.</span>
Correct option is third 
<h3><u>Solution:</u></h3>
Given that:

Need to check which of the expression from given four expressions will be true.
Let's first try to eliminate wrong options.
If we observe carefully, we can say that option 2 that is
is not correct as
must be equal to
and not 
Lets now modify given expression that is:

On adding 1 to both sides we get


Hence correct option is third one that is
(3.6*100)/6=60
(1.8*100)/6=30
60*30=1800
there are 1800 pictures could fit on the wall.