Question

John can run the 100 meters dash in 16 1/5 seconds. Savanna’s best time is 19.8 seconds. How much faster is John than savanna in the 100 meter dash

Answer 1

Given that

                                                                  1

John can run 100 meters dash in 16    --------- seconds .

                                                                   5

Savanna 's time is 19.8 seconds .

Here we have John time in mixed fraction and Savanna's time in decimal .

Converting mixed fraction into improper .

      1                      16 * 5     +  1                 80 + 1                 81

16  --------    =     ---------------------------    =   -------------- =   - -----------

     5                           5                                  5                      5

Thus we got John time as 81 /5 seconds .

Converting Savanna's time in fraction , we get

 19 8

----------  seconds .

   10  

We have two fractions with different denominator .

One is having denominator 5 and another is having denominator 10 .

We need to make the denominator same of both the fraction .

We need to make denominator 10 .

Multiply John fraction by 2 in both numerator and denominator by 2 to make denominator 10 .

81 * 2               162

----------  =      ------------ seconds .

5 *  2                   10

John is taking less time than Savanna . Thus John is faster .

Difference

198          162            36

-------  -     -------     =  ------- seconds  

10              10              10

Thus John is faster by  (36/10 ) seconds  =  3.6 seconds  .