Physical science : find the speed of an object that covers 400 km in 5 hr.
a. 40 km/hr
b. 80 km/hr
c. 2000 km/hr
d. 800 km/hr

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)

5   1/4   miles per hour

step-by-step explanation:

15   3/4 / 3 = 5   1/4