Chapter 1: Knowing your numbers (Solutions)
Posted on : 05-11-2017

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EXERCISE 1.1

1. Fill in the blanks

(a) 1 lakh = 10 ten thousand.

(b) 1 million = 10 hundred thousand.

(c) 1 crore = 10 ten lakh.

(d) 1 crore = 10 million.

(e) 1 million = 10 lakh.

2. Place commas correctly and write the numerals

  1. Seventy three lakh seventy five thousand three hundred seven → 73, 75, 307
  2. Nine crore five lakh forty one → 9, 05, 00, 041
  3. Seven crore fifty two lakh twenty one thousand three hundred two → 7, 52, 21, 302
  4. Fifty eight million four hundred twenty three thousand two hundred two → 58, 423, 202
  5. Twenty three lakh thirty thousand ten → 23, 33, 010

3. Insert commas suitably and write the names according to Indian System of Numeration

(a) 87595762 (b) 8546283 (c) 99900046 (d) 98432701

Answer:

  1. 8,75,95,762 – Eight crore seventy five lakh ninety five thousand seven hundred sixty two
  2. 85,46,283 – Eighty five lakh forty six thousand two hundred eighty three
  3. 9,99,00,046 – Nine crore ninety nine lakh forty six
  4. 9,84,32,701 – Nine crore eighty four lakh thirty two thousand seven hundred one

Insert commas suitably and write the names according to International System of Numeration

(a) 78921092 (b) 7452283 (c) 99985102 (d) 48049831

Answer:

  1. 78,921,092 – Seventy eight million nine hundred twenty one thousand ninety two
  2. 7,452,283 – Seven million four hundred fifty two thousand two hundred eighty three
  3. 99,985,102 – Ninety nine million nine hundred eighty five thousand one hundred two
  4. 48,049,831 – Forty eight million forty nine thousand eight hundred thirty one

EXERCISE 1.2

1. A book exhibition was held for four days in a school. The number of tickets sold at the counter on the first, second, third and final day was respectively 1094, 1812, 2050 and 2751. Find the total number of tickets sold on all the four days.

Answer: The total number of tickets sold on all the four days = 1094 + 1812 + 2050 + 2751 = 7707

2. Shekhar is a famous cricket player. He has so far scored 6980 runs in test matches. He wishes to complete 10,000 runs. How many more runs does he need?

Answer: Runs needed by Shekhar to complete 10,000 = 10,000 – 6980 = 3020

3. In an election, the successful candidate registered 5, 77, 500 votes and his nearest rival secured 3, 48, 700 votes. By what margin did the successful candidate win the election?

Answer: The successful candidate won the election by margin = 5, 77, 500 – 3, 48, 700 = 1, 28, 800 votes

4. Kirti bookstore sold books worth Rs 2, 85, 891 in the first week of June and books worth Rs 4, 00, 768 in the second week of the month. How much was the sale for the two weeks together? In which week was the sale greater and by how much?

Answer: The sale for the two weeks together = 2, 85, 891 + 4, 00, 768 = Rs 6, 86, 659

In the second week of month sale was greater and it was by Rs = 4, 00, 768 -2, 85, 891 = 1, 14, 877

 5. Find the difference between the greatest and the least number that can be written using the digits 6, 2, 7, 4, 3 each only once.

Answer: Greatest number using given digit = 76, 432

Lowest number using given digit = 23, 467

Difference between greatest and lowest = 76, 432 – 23, 467 = 52, 965

6. A machine, on an average, manufactures 2,825 screws a day. How many screws did it produce in the month of January 2006?

Answer: The number of days in the January = 31

Therefore, the screws produced in the month January = 31 × 2825 = 87575

 7. A merchant had Rs 78,592 with her. She placed an order for purchasing 40 radio sets at Rs 1200 each. How much money will remain with her after the purchase?

Answer: The money spend for order = 40 × 1200 = 48,000

The money left with her after the purchase = 78,592 – 48,000 = Rs 30,592

8. A student multiplied 7236 by 65 instead of multiplying by 56. By how much was his answer greater than the correct answer? (Hint: Do you need to do both the multiplications?)

Answer: Incorrect answer = 7236 × 65 = 4, 70, 340

Correct answer = 7236 × 56 = 4, 05, 216

Incorrect answer is greater than correct answer by = 4, 70, 340 – 4, 05, 216 = 65, 124

9. To stitch a shirt, 2 m 15 cm cloth is needed. Out of 40 m cloth, how many shirts can be stitched and how much cloth will remain? (Hint: convert data in cm.)

Answer:  We know, 1 m = 100 cm

The cloth needed to stitch shirt in cm = (2 × 100) + 15 = 215 cm

The total cloth available in cm = 40 × 100 = 4000 cm

The number of shirts can be stitched from available cloth will be total cloth available divided by cloth needed to stitch a shirt and remainder will be cloth remained.

4000215=18.6

It means 18 shirts can be stitched. 130 cm cloth will remain.

10. Medicine is packed in boxes, each weighing 4 kg 500g. How many such boxes can be loaded in a van which cannot carry beyond 800 kg?

Answer: Medicine box weight in g = (4 × 1000) + 500 = 4500 g

Maximum load van can carry in g = 800 × 1000 = 8, 00, 000 g

The no. of boxes can be loaded = 8000004500=177.7

Therefore, maximum 177 boxes can be loaded.

11. The distance between the school and the house of a student’s house is 1 km 875 m. Every day she walks both ways. Find the total distance covered by her in six days.

Answer: The distance between the school and the house of a student’s house in m = 1875 m

Therefore, per day she covers a distance in m = 1875 × 2 = 3750 m

The total distance covered by her in six days = 3750 × 6 = 22500 m i.e. 22 km 500 m

12. A vessel has 4 liters and 500 ml of curd. In how many glasses, each of 25 ml capacity, can it be filled?

Answer: A vessel has 4500 ml of curd. The glass capacity is 25 ml.

The no. of glasses can be filled = 450025=180 ml


EXERCISE 1.3

1. Estimate each of the following using general rules

To get a closer estimate, let us try rounding each number to hundreds.

a) 730 + 998 → 700 + 1000 = 1700

b) 796 – 314 → 800 + 300 = 1100

c) 12,904 + 2,888 → 13000 + 3000 = 16000

d) 28,292 – 21,496 → 28300 + 21500 = 49800

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

Answer: 

Rough estimate 400 + 300 + 4300 = 5000

Closer estimate 440 + 330 + 4320 = 5090

b) 1,08,734 – 47,599

Answer: 

Rough estimate 108700 – 47600 = 61100

Closer estimate 108730 – 47600 = 61130

c) 8325 – 491

Answer: 

Rough estimate 8300 – 500 = 7800

Closer estimate 8330 – 490 = 7840

d) 4,89,348 – 48,365

Answer: 

Rough estimate  4, 89,300 – 48, 400 = 440900

Closer estimate 4, 89, 350 – 48, 370 = 440980

 3. Estimate the following products using general rule

a) 578 × 161

Answer: 600 × 200 =120000

b) 5281 × 3491

Answer: 5000 × 3000 = 15000000

c) 1291 × 592

Answer: 1000 × 600 = 600000

d) 9250 × 29

Answer:  9000 × 30 = 270000



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