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
The cost of my me knife is $5.52
Answer:
the slope equals 2. otherwise known as the coefficient of x.
Answer:
No, modern train cannot travel on old railroad.
Step-by-step explanation:
In rail transport, track gauge is the spacing of the rails on a railway track and is measured between the inner faces of the load-bearing rails.
Most of the modern train are based on broad gauge. The separation in broad gauge is about 5 ft and 6 inches and in the standard gauge the separation between the tracks is 4 ft and
inches. So for the modern train it is not possible to travel on the tracks whose separation is no more than 4.5 feet.