Roxie and Estu are estimating the values of simple expressions Class 7

Roxie and Estu are estimating the values of simple expressions Class 7

Roxie and Estu are estimating the values of simple expressions Class 7

Question 1.

4,63,128 + 4,19,682,

Roxie: “The sum is near 8,00,000 and is more than 8,00,000.”

Estu: “The sum is near 9,00,000 and is less than 9,00,000.” Class 7

(a) Are these estimates correct? Whose estimate is closer to the sum?

(b) Will the sum be greater than 8,50,000 or less than 8,50,000? Why do you think so?

(c) Will the sum be greater than 8,83,128 or less than 8,83,128? Why do you think so?

(d) Exact value of 4,63,128 + 4,19,682 = _________

Solution:

(a) Yes, Estu’s estimate is closer to the sum.

(b) Greater than 8,50,000.

Because 63 + 19 > 50.

(c) Less than 8,83,128. Because 63 + 19 = 82 and here 82 < 83 and also 682 < 1000.

(d) 8,82,800 (Exact value)

Question 2.

14,63,128 - 4,90,020

Roxie: “The difference is near 10,00,000 and is less than 10,00,000.”

Estu: “The difference is near 9,00,000 and is more than 9,00,000.” Class 7

(a) Are these estimates correct? Whose estimate is closer to the difference?

(b) Will the difference be greater than 9,50,000 or less than 9,50,000? Why do you think so?

(c) Will the difference be greater than 9,63,128 or less than 9,63,128? Why do you think so?

(d) Exact value of 14,63,128 - 4,90,020 = _____________

Solution:

(a) Yes, Roxie’s estimate is closer to the difference.

(b) Greater than 9,50,000. Because 1463 - 490 = 973, which is greater than 950.

(c) Greater than 9,63,128. Because 1463 - 490 = 973, which is greater than 963.

(d) 9,73,108 (Exact value)