By rounding to 1 significant figure, estimate
102.2 x 4.2

ANSWER: 400

EXPLANATION:

1) 102.2 rounded to 1 significant figure = 100

2) 4.2 rounded to 1 significant figure = 4

3) Therefore, we multiply 100 by 4, which equals 400.

EXAMPLES + EXPLANATION (IF NEEDED TO UNDERSTAND MORE)

Rounding to 2 significant figures:

102.2 = 1.0 x (we have to write it in scientific notation because it's the only way. If the number was 105 or higher, we'd be able to round it and write it as 110 but this isn't the case)4.2 = 4.2 (already in 2 significant figures)

Rounding to 3 significant figures:

102.2 = 102 4.2 = 4.20 (the 0 counts as a significant figure because there is a decimal)

Rounding to 4 significant figures:

102.2 = 102.2 (already in 4 significant figures)4.2 = 4.200 (the two 0s count as significant figures because there is a decimal)