2. Give a rough estimate (by rounding off to nearest hundreds) and also a closer estimate
(by rounding off to nearest tens):
(a) 439 + 334 + 4,317 (b) 1,08,734 - 47,599 (c) 8325 - 491
(d) 4,89,348 - 48,365
Make four more such examples.
Answers
(a) 439+334+4,317439+334+4,317
Rough estimate-
439+334+4,317\ \Rightarrow400+300+4,300\ =5,000439+334+4,317 ⇒400+300+4,300 =5,000
Closer estimate-
439+334+4,317\ \Rightarrow440+330+4,320\ \Rightarrow\ 5,090439+334+4,317 ⇒440+330+4,320 ⇒ 5,090
(b) 1,08,734-47,5991,08,734−47,599
Rough estimate-
1,08,734-47,599\ \Rightarrow1,08,700-47,600\ \Rightarrow61,1001,08,734−47,599 ⇒1,08,700−47,600 ⇒61,100
Closer estimate-
1,08,734-47,599\ \Rightarrow1,08,730-47,600\ =61,1301,08,734−47,599 ⇒1,08,730−47,600 =61,130
(c) 8,325-4918,325−491
Rough estimate-
8,325-491\ \Rightarrow8,300-500\ =7,8008,325−491 ⇒8,300−500 =7,800
Closer estimate-
8,325-491\ \Rightarrow8,330-490\ =7,8408,325−491 ⇒8,330−490 =7,840
(d) 4,89,348-48,3654,89,348−48,365
Rough estimate-
4,89,348-48,365\ \Rightarrow4,89,300-48,400\ =4,40,9004,89,348−48,365 ⇒4,89,300−48,400 =4,40,900
Closer estimate-
4,89,348-48,365\ \Rightarrow4,89,350-48,370\ =4,40,9804,89,348−48,365 ⇒4,89,350−48,370 =4,40,980
Four more such examples:
Example 1: 484+662484+662
Rough estimate-
484+662\ \Rightarrow500+700\ =1,200484+662 ⇒500+700 =1,200
Closer estimate-
484+662\ \Rightarrow480+660\ =1,140484+662 ⇒480+660 =1,140
Example 2: 8,768-3,8178,768−3,817
Rough estimate-
8,768-3,817\ \Rightarrow8,800-3,800\ =5,0008,768−3,817 ⇒8,800−3,800 =5,000
Closer estimate-
8,768-3,817\ \Rightarrow8,770-3,820\ =4,9508,768−3,817 ⇒8,770−3,820 =4,950
Example 3: 6,763+9,7656,763+9,765
Rough estimate-
6,763+9,765\ \Rightarrow6,800+9,800\ =16,6006,763+9,765 ⇒6,800+9,800 =16,600
Closer estimate-
6,763+9,765\ \Rightarrow6,760+9,770\ =16,5306,763+9,765 ⇒6,760+9,770 =16,530
Example 4: 3,828-1,2823,828−1,282
Rough estimate-
3,828-1,282\ \Rightarrow3,800-1,300\ =2,5003,828−1,282 ⇒3,800−1,300 =2,500
Closer estimate-
3,828-1,282\ \Rightarrow3,830-1,280\ =2,5503,828−1,282 ⇒3,830−1,280 =2,550
(a) 439+334+4317
Give a rough estimate (by rounding off to nearest hundreds) and also a closer estimate
(by rounding off to nearest tens):
(a) 439 + 334 + 4,317 (b) 1,08,734 - 47,599 (c) 8325 - 491
(d) 4,89,348 - 48,365
I think it's helpful to you