Question

How many seconds are there in 3 days?
A.259200 s
B.172800 s
C.24800 s
D.72000 s

Answer 1

Hint: This question can easily be solved using the facts that how many seconds are in a minute, how many minutes are there in an hour and how many hours are there in a day. Hence, we would easily be able to find how many seconds are there in 3 days by just multiplying these facts correctly without making any kind of calculation mistakes.

Complete step-by-step answer:
Now, as we know, there are 60 seconds in 1 minute.
\[ \Rightarrow 1{\rm{ min = }}60{\rm{ s}}\]
Also, in 1 hour, there are 60 minutes
\[ \Rightarrow 1{\rm{ hour = }}60{\rm{ min}}\]
Hence, from both the sentences, we know that in \[1\] hour, there are \[60\] minutes and in \[1\] minute there are \[60\]seconds.
Hence,
\[1{\rm{ hour = }}60{\rm{ }} \times {\rm{ 60 s}}\]
\[ \Rightarrow 1{\rm{ hour = 3600 s}}\]
Now, in \[1\] day, there are \[24\] hours.
Hence, total seconds in a day would be:
\[1{\rm{ day = }}24{\rm{ hours = 24}} \times {\rm{3600 s}}\]
\[ \Rightarrow 1{\rm{ day = 86400 s}}\]
Now, since, in a day there are \[86400\] seconds.
Hence, total number of seconds in 3 days will be:
\[{\rm{3 days = 3}} \times {\rm{ 86400 s}}\]
\[ \Rightarrow {\rm{3 days = 259200 s}}\]
Hence, option A is the correct option.

Note: This question can also be solved using the ‘Unit Factor Method’ which means that if we multiply any expression or number by ‘one’, then the expression or number would remain unchanged, i.e. their value would not be affected.
First of all, we would write all the basic facts related to this question that we know, i.e.
\[1{\rm{ day = }}24{\rm{ hours }}\]
\[1{\rm{ hour = }}60{\rm{ min}}\]
\[1{\rm{ min = }}60{\rm{ s}}\]
Now, using Unit Factor, we can write all the above three facts as:
\[\dfrac{{24{\rm{ hours }}}}{{1{\rm{ day}}}} = 1\]
\[\dfrac{{60{\rm{ min}}}}{{1{\rm{ hour }}}} = 1\]
\[\dfrac{{60{\rm{ s}}}}{{1{\rm{ min}}}} = 1\]
Now, we have to find out how any seconds are there in 3 days.
\[ \Rightarrow 3{\rm{ days = }}3{\rm{ days}} \times \dfrac{{24{\rm{ hours }}}}{{1{\rm{ day}}}} \times \dfrac{{60{\rm{ min}}}}{{1{\rm{ hour }}}} \times \dfrac{{60{\rm{ s}}}}{{1{\rm{ min}}}}\]
Now, we will eliminate days, hours and min from numerator and denominator respectively (as they will cancel out with each other)
\[ \Rightarrow 3{\rm{ days = }}3 \times 24 \times 60 \times 60{\rm{ s}}\]
\[ \Rightarrow 3{\rm{ days = 259200 s}}\]
Hence, option A is the correct answer.
We can solve this question using either of the two ways.