Q.1 Estimate each of the following using general rule:
(a) 730 + 998 (b) 796 – 314 (c) 12904 + 2888 (d) 28292 – 21496
Make ten more such examples of addition, subtraction and estimation of their outcome.


Answer :

(a) 730 + 998
Round off to hundreds
730 rounds off to 700
998 rounds off to 1000
Hence, 730 + 998 = 700 + 1000 = 1700
(b) 796 – 314
Round off to hundreds
796 rounds off to 800
314 rounds off to 300
Hence, 796 – 314 = 800 – 300 = 500
(c) 12904 + 2888
Round off to thousands
12904 rounds off to 13000
2888 rounds off to 3000
Hence, 12904 + 2888 = 13000 + 3000 = 16000
(d) 28292 – 21496
Round off to thousands
28292 round off to 28000
21496 round off to 21000
Hence, 28292 – 21496 = 28000 – 21000 = 7000
Ten more such examples are
(i) 540 + 360 = 500 + 400 = 900
(ii) 7657 + 4450 = 8000 + 4000 = 12000
(iii) 9892 – 2372 = 10000 – 2000 = 8000
(iv) 9740 – 2002 = 10000 – 2000 = 8000
(v) 2678 + 1111 = 3000 + 1000 = 4000
(vi) 1110 – 1222 = 1000 – 1000 = 0
(vii) 980 + 525 = 1000 + 500 = 1500
(viii) 7400 + 4300 = 7000 + 4000 = 11000
(ix) 6831 + 2222= 7000 + 2000 = 9000
(x) 9285 + 1119 = 9000 + 1000 = 10000

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