Question 286433
Recall that distance = rate*time or D = rt



In this case, D=60 cm and {{{r = 2.4*10^10}}} cm/sec. Plug these values in to get {{{60=2.4*10^10t}}}



Now divide both sides by 2.4 to get {{{25=10^10t}}}



Now divide both sides by {{{10^10}}} to isolate 't' to get {{{t=25/(10^10)}}}



From here, it helps to remember that negative exponents effectively flip fractions. Eg. {{{(2/3)^(-2)=(3/2)^2}}}. This means that we can write {{{t=25/(10^10)}}} as {{{t=25/(10^10)=25*10^(-10)=2.5*10^(-9)}}} 



So the value of 't' is {{{t=2.5*10^(-9)}}} seconds. Now just multiply this answer by {{{1/(10^(-9))}}} (this is the given conversion factor) to convert the answer into nanoseconds to get {{{t=(2.5*10^(-9))(1/(10^(-9)))=(2.5*10^(-9))/(10^(-9))=2.5*10^0=2.5*1=2.5}}}  nanoseconds



So it takes about 2.5 nanoseconds.