Think of it this way: when you write a mixed number, the fraction is out of 100. If the denominator is 8, find 1/8 of 100 by doing 100 divided by 1/8. This gives you 12.5. The entire fraction is 2/8, so we need to multiply 12.5 by 2, since it's only 1/8. 12.5 x 2 gives us 25. In the decimal, this would be equal to .25. A is the only answer that represents the mixed number as a decimal correctly.
It would take 110 seconds or a minute and 40 seconds. 400 divided by 50 = 4...... 27.5 multiplied by 4 equals 110; therefore, the answer is mike would swim 400 meters in 110 seconds.
