Note: a radioactive decay constant is always negative.
time = [natural log(ending amount / beginning amount)] / k
time = ln (20 / 24) / -.00011
time = ln (5/6) / -.00011
time = -.018232155683 / -.00011
time =
<span>
<span>
<span>
165.7468698455
</span>
</span>
</span>
time =
<span>
<span>
<span>
165.75 years
</span></span></span>
Assuming 0 and 100 are included in the possible choices:
There are

multiples of 7 between 0 and 100, so there is a

probability of choosing a multiple of 7.
Length: 3 yds. 36 in= 1 yd; 108 in.=3 yds
Width: 4 ft. 12 in=1 ft.; 48 in= 4 ft.
Sinve there are two lengths and widths in a rectangle, I like to multiply them both by 2 and add up the results. You also get the same answer when you add everything up twice. My answer is 312 in.