I hope this helped I've only done part A
Answer:

Step-by-step explanation:
we are given half-life of PO-210 and the initial mass
we want to figure out the remaining mass <u>after</u><u> </u><u>4</u><u>2</u><u>0</u><u> </u><u>days</u><u> </u>
in order to solve so we can consider the half-life formula given by

where:
- f(t) is the remaining quantity of a substance after time t has elapsed.
- a is the initial quantity of this substance.
- T is the half-life
since it halves every 140 days our T is 140 and t is 420. as the initial mass of the sample is 5 our a is 5
thus substitute:

reduce fraction:

By using calculator we acquire:

hence, the remaining sample after 420 days is 0.625 kg
Answer:
J. 12 : 18
Step-by-step explanation:
Amy used 2 tea bags for every 3 cups of water to make iced tea
the ratio here is 2:3
x = 2:3
lets simplify our ratios
6 : 10 = 3 : 5 ≠ 2 : 3
5 : 6 = (doesn't simplify evenly) ≠ 2 : 3
9 : 15 = 3 : 5 ≠ 2 : 3
12 : 18 = 2 : 3 = 2 : 3
<h3>
Simplifying</h3>
find their highest common factor and divide both the numbers by the <u>same amount</u> (HCF).
Ex.
12 : 18
12 ÷ 6 = 2
18 ÷ 6 = 3
2 : 3
1 in 14 or 1/14
this is the formula I used to calculate:
Probability = Favorable cases / Possible cases
Multiply straight across and then just simply your answer. I divided by 2.