Answer:
Its either C. or D.
Step-by-step explanation:
Answer:
(a) A = (20mg)/(2^(t/30))
(b) 12.6mg
(c) 129.6years
Step-by-step explanation:
To calculate the amount remaining after a number of half-lives, n, we can make use of:

Where A = amount remaining
B = initial amount

(a) A = (20mg)/(2^(t/30))
(b) Mass after 20years
A = (20mg)/(2^(20/30)) ≈ 12.6mg
(c) After how long will only 1mg remain:
1mg = (20mg)/(2^(t/30))

Taking log of both sides we have:
Log(20) = (t/30)log(2)
t/30 = (log(20))/(log(2)) ≈ 4.3
t/30 = 4.3
t = 30 x 4.3 ≈ 129.6years.
Answer:It’s. B
Step-by-step explanation:
Answer:
502m
Step-by-step explanation:
let x and y represent the length and breadth of rectangular meadow respectively.
Given,
Perimeter of the meadow =1004m
or,2(l+b)=1004m
or2(x+y)=1004m
orx+y=1004m/2
or,x+y=502m
i.e sum of length and breadth
Just count the zeros at the left. In your case <span>6
</span> so your number equals <span><span>0.428⋅<span>10<span>−6</span></span></span>
</span> and in scientific <span>4.28⋅<span>10<span>−<span>7</span></span></span></span>