The product of all the prime numbers less than 20 is closest to which of the following powers of 10 ?  Choose the correct choice from the following
A) 10^9	B) 10^8	C) 10^7	D) 10^6	E) 10^5
We should find the approximate value of 2*3*5*7*11*13*17*19 to some power of 10.   # of different approximations are possible.   Approach #1:    2*5= 
<gadget id="calculator"> 2*5</gadget>
<output>10</output>
10;   3*7=~20 (actually more than 20);   11*19=~200 (actually more than 200);   13*17=~200 (actually more than 200);   2∗3∗5∗7∗11∗13∗17∗19≈10∗20∗200∗200=8∗106≈107   Answer: C.   Approach #2:    2*5= 
<gadget id="calculator"> 2*5</gadget>
<output>10</output>
10   3*17=~50 (actually more than 50);   7*13=~100 (actually less than 100);   11*19=~200 (actually more than 200)   2∗3∗5∗7∗11∗13∗17∗19≈10∗50∗100∗200=107.   Answer: 10^7.
<result>C</result>
The product of all the prime numbers less than 20 is closest to which of the following powers of 10 ?