Answer:
20.20
Step-by-step explanation:
The answer is 4 feet which equals to 48 inches and the remaining inches are 7 inches
Amount remaining = Beginning Amount / (2^n)
where n = elapsed time / half-life
Amount remaining = 641 kg / (2^[4/68])
Amount remaining = 641 kg / (2 ^
<span>
<span>
<span>
0.0588235294
</span>
</span>
</span>
)
Amount remaining = 641 kg /
<span>
<span>
<span>
1.0416160107
</span>
</span>
</span>
Amount remaining =
<span>
<span>
<span>
615.3</span></span></span>90 kg
You'll find this link helpful
<span>
<span>
</span></span>http://www.1728.org/halflife.htm