Estimate each of the following by rounding off each number nearest to its greatest place:

(i) 730 + 998

(ii) 5,290 + 17,986

(iii) 796 - 314

(iv) 28,292 - 21,496

(i) 730 + 998

Rounding off 730 to its greatest place (hundreds): tens digit is 3 (< 5), so 730 → 700.

Rounding off 998 to its greatest place (hundreds): tens digit is 9 (≥ 5), so 998 → 1000.

Estimated sum = 700 + 1000 = 1,700.

Hence, the estimated sum = 1,700.

(ii) 5,290 + 17,986

Rounding off 5,290 to its greatest place (thousands): hundreds digit is 2 (< 5), so 5,290 → 5,000.

Rounding off 17,986 to its greatest place (ten thousands): thousands digit is 7 (≥ 5), so 17,986 → 20,000.

Estimated sum = 5,000 + 20,000 = 25,000.

Hence, the estimated sum = 25,000.

(iii) 796 - 314

Rounding off 796 to its greatest place (hundreds): tens digit is 9 (≥ 5), so 796 → 800.

Rounding off 314 to its greatest place (hundreds): tens digit is 1 (< 5), so 314 → 300.

Estimated difference = 800 - 300 = 500.

Hence, the estimated difference = 500.

(iv) 28,292 - 21,496

Rounding off 28,292 to its greatest place (ten thousands): thousands digit is 8 (≥ 5), so 28,292 → 30,000.

Rounding off 21,496 to its greatest place (ten thousands): thousands digit is 1 (< 5), so 21,496 → 20,000.

Estimated difference = 30,000 - 20,000 = 10,000.

Hence, the estimated difference = 10,000.