The best way to really predict the outcome of multiplying 750 by 0.1 without calculator is firstly, converting the decimal to a fraction to easily do the multiplication in your head.
Since one of the multiplicand is a decimal the products will be much complicated therefore, to convert the decimal number 0.1 to a fraction number we shift the point to the right hand side which simply translate to 1/10. The trick here is the number of times we shift the point will determine the number of zeros the denominator will possess. Assuming we have 0.12 as the decimal, it is required we shift the point twice and the resulting value we become 12/100. If the decimal is 0.123 it is required we shift the point 3 times , the resulting value will be 123/1000. Not the number of times we shift the point will determine the number of zero's of the denominator.
Finally, the 2 multiplicands are now 750 and 1/10 which is more easier to manipulate in our head.
750 × 1/10 = 750/10 = 75( you just cancel the zeros)
We know that "T" is the total time for driving and hiking and "x" is the average velocity on the hike.
Knowing that the tourist drives 70 miles along the scenic highway and walk 7-mile walk along the hiking trail, and also knowing that the average velocity driving is 7 times that while hiking, we can conclude that the total time is:
Finally, simplifying the equation, we get that the total time for driving and hiking as a function of the average velocity on the hike, is: