Question

Let us round off these numbers to nearest hundreds. Estimated difference 54900-54600=300 Hence, we need to be careful in estimating the giver ers Exercise 1.4 1. Round off the following numbers to nearest ten : (i) 58 (ii) 619 (iii) 232 2. Round off the following numbers to nearest thousand : (1) 2934 (ii) 2764 (iii) 7956 3. Round off following numbers to nearest lakh : (i) 65321 (ii) 254305 Maths 61245 ​

Answer 1

Answer:

(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

Answer 2

Explanation:

order to estimate to nearest hundreds we follow the following procedure:

Step I: Obtain the number.

Step II: Examine the digit at tens place.

Step III: If the digit at tens place is less than 5, replace each one of the digits at tens and ones or units place by 0 and keep all other digits as they are.

If the digit at tens place is 5 or greater than 5, increase the digit at hundreds place by 1 and replace each one of the digits at tens and ones place by 0.

The number so obtained is the number rounded off to the nearest hundreds.