Estimate each of the following products by rounding off each number to the nearest ten:

(i) (49 × 72)

(ii) (39 × 62)

(iii) (63 × 57)

(iv) (35 × 43)

(i) (49 × 72)

Round 49 to the nearest ten: The units digit is 9, so it rounds up to 50.

Round 72 to the nearest ten: The units digit is 2, so it rounds down to 70.

Approximate product: 50 × 70 = 3,500

Hence, the approximate product = 3,500.

(ii) (39 × 62)

Round 39 to the nearest ten: The units digit is 9, so it rounds up to 40.

Round 62 to the nearest ten: The units digit is 2, so it rounds down to 60.

Approximate product: 40 × 60 = 2,400

Hence, the approximate product = 2,400.

(iii) (63 × 57)

Round 63 to the nearest ten: The units digit is 3, so it rounds down to 60.

Round 57 to the nearest ten: The units digit is 7, so it rounds up to 60.

Approximate product: 60 × 60 = 3,600

Hence, the approximate product = 3,600.

(iv) (35 × 43)

Round 35 to the nearest ten: The units digit is 5, so it rounds up to 40.

Round 43 to the nearest ten: The units digit is 3, so it rounds down to 40.

Approximate product: 40 × 40 = 1,600

Hence, the approximate product = 1,600.