Rubidium-87 Decays by Beta Decay with a Half-Life of 4

question 57

Multiple Choice

Rubidium-87 decays by beta decay with a half-life of 4.9 * 10¹⁰ yr. How many ⁸⁷Rb atoms are in a moon rock sample that has a rubidium decay rate of 3,500 disintegrations per hour

• A) 9.0 * 10¹⁶ atoms
• B) 4.3 * 10^-4 atoms
• C) 2.2 * 10¹⁸ atoms
• D) 2.5 * 10¹⁴ atoms
• E) 1.7 * 10¹⁴ atoms