A rock sample contains 1/2 microgram of the parent radioactive ...

[ereecah]

A rock sample contains 1/2 microgram of the parent radioactive isotope U-235 and 1/2 microgram of its daughter isotope Pb-207. If the half-life of this decay is 700 million years, how old is this rock?
 
  A) 1400 million years
  B) 2100 million years
  C) 700 million years
  D) 350 million years

Question 2

A current reading is obtained by properly placing an ammeter in a circuit consisting of one resistor and one battery. As a result
 
  A) the voltage drop across the resistor increases.
  B) the current flowing in the circuit increases.
  C) the current flowing in the circuit decreases.
  D) the current flowing in the circuit does not change.

[Bigfoot1984]

Answer to Question 1

C

Answer to Question 2

C

[ereecah]

Wow, this really help

[Joy Chen]

Excellent