8.4. To come to this conclusion, one must remember that 1/10 of a number is in essence saying this is 1 out of 10 equally divided portions of a number. This is equivalent to 10%. Multiply the number by the denominator, in this case 10, and you will get the total number. 0.84 x 10 = 8.4 (10% x 10 = 100%). Another way to look at it is to add 0.84 ten times. Either way you should end up with 8.4.