Answer:
39
Explanation:
To estimate the value of 77.8 x 0.49, we can round each number to a more manageable value and then perform the multiplication.
Rounding 77.8 to the nearest whole number gives us 78, and rounding 0.49 to the nearest tenth gives us 0.5
Noting that 0.5 is 1/2
78 x 0.5 is the same as taking half of 78
78/2 = 39
So the estimate of 77.8 x 0.49 is 39
(Note that the actual value of 77.8 x 0.49 is 38.122 so there is an estimate error of 0.878 which works out to an error percentage of 2.3%)