Uranium-238 $${ } _ { 92 } ^ { 238 } \mathrm { U }$$

question 78

Multiple Choice

Uranium-238 ( $${ } _ { 92 } ^ { 238 } \mathrm { U }$$ ) decays to form thorium-234 ( $${ } _ { 90 } ^ { 234 } \mathrm { Th }$$
) with a half-life of 4.5 *10⁹ years. How many years will it take for 75% of the uranium-238 to decay?

• A) 9.0 * 10¹⁰ years
• B) 4.5 * 10⁹ years
• C) 4.5 * 10¹⁰ years
• D) 9.0 *10⁹ years
• E) 3.8* 10⁹ years