rational numbers help

Edit

Both are rational

For the first, we have   4 + 21/99  = 4 + 7/33 =  139/33

For the second, we have   2.78   =  2 + 78/100   =  278/100  = 139/50

Thanks, guys, for pointing out my earlier error.....however.....the "Guest's" answer of 41/100  is not correct because the "21" part does not repeat

Check to see that 139/33 results in a "repeating"  decimal part of "21"

a- Is a rational because you can write it as a ratio 4.21=4 21/100=421/100

b- Is a rational because you can write it as a ratio 2.78=2 39/50  =139/50

Note: CPhill first answer about 4.21 is incorrect. The "Guest" first answer is correct.