Question

Sam is comparing the half-life of two isotopes of uranium. The half-life of Uranium-238 is 4.5×109
4.5
×
10
9
years. The half-life of Uranium-233 is 1.6×105
1.6
×
10
5
years. He computed how much greater the half-life of Uranium-238 is than that of Uranium-233, and his calculator displayed the number 2.81E4. What is this number in scientific notation?(1 point)
Responses

2.81+104
2.81
+
10
4

2.81 plus 10 superscript 4 baseline

4×102.81
4
×
10
2.81

4 times 10 superscript 2.81 baseline

2.81×10−4
2.81
×
10
−
4

2.81 times 10 superscript negative 4 baseline

2.81×104

Answer 1

2.81 × 10^4

(2.81E4 means 2.81 × 10^4; indeed (4.5×10^9)/(1.6×10^5) = 2.8125×10^4 ≈ 2.81×10^4.)