7th Maths : Term 1 Unit 1 : Number System : Exercise 1.5 ; Text Book Back Exercises Questions with Answers, Solution

**Exercise 1.5**

** **

**1. One night in
Kashmir, the temperature is −5º C. Next day the temperature is 9º C. What is
the increase in temperature?**

9°C – (–5°C) = 9°C + 5°C =
14°C

** **

**2. An atom can
contain protons which have a positive charge ( +) and electrons which have a
negative charge ( −) . When an electron and a proton pair up, they become
neutral (0) and cancel the charge out. Now, Determine the net charge:**

**(i) 5 electrons and
3 protons → −5 + 3 = −2 that is 2 electrons **

**(ii) 6 Protons and 6
electrons →**

**(iii) 9 protons and
12 electrons →**

**(iv) 4 protons and 8
electrons →**

**(v) 7 protons and 6
electrons →**

** **

**3. Scientists use
the Kelvin Scale (K) as an alternative temperature scale to degrees**

**Celsius (°C) by the
relation T º C = ( T + 273) K.**

**Convert the
following to kelvin:**

**(i) −275° C (ii) 45°
C (iii) −400° C (iv) −273° C**

**(i) –275° C**

(–275 + 273) K = –2° K

**(ii) 45°C**

(45 + 273) K = 318° K

**(iii) –400° C**

(–400 +273) K = 127° K

**(iv) –273°C**

(–273 + 273)K = 0° K

** **

**4. Find the amount
that is left in the student’s bank account, if he has made the following
transaction in a month. His initial balance is ₹ 690.**

**(i) Deposit ( +) of
₹ 485**

**(ii) Withdrawal ( −)
of ₹ 500**

**(iii) Withdrawal (
−) of ₹ 350**

**(iv) Deposit ( +) of
₹ 89**

**(v) If another ₹ 300
was withdrawn, what would the balance be?**

**(i) Deposit (+) of ₹
485 ? **

₹ 690 + ₹ 485 = ₹ 1175

**(ii) Withdrawal (–)
of ₹ 500 ? **

₹ 1175 – ₹ 500 = ₹ 675

**(iii) Withdrawal (–)
of ₹ 350**

₹ 675 – ₹ 350 = ₹ 325

**(iv) Deposit of (+)
₹ 89 **

₹ 325 + ₹ 89 = ₹ 414

**(v) If another ₹ 300
was withdrawn, what would the balance be? **

₹ 414 – ₹ 300 = ₹ 114

The balance would be = ₹ 114

** **

**5. A poet Tamizh
Nambi lost 35 pages of his ‘lyrics’ when his file had got wet in the rain. Use
integers, to determine the following:**

**(i) If Tamizh Nambi
wrote 5 page per day, how many day’s work did he lose?**

35 ÷ 5 = 7 days

**(ii) If four pages
contained 1800 characters, (letters) how many characters were lost?**

4 pages contained characters = 1800

∴ 35 pages contained characters = [ 1800 × 35 ] / 4 = 15750

**15750 characters
were lost**

**(iii) If Tamizh
Nambi is paid ₹250 for each page produced, how much money did he lose?**

Paid money for 1 page = ₹ 250

Paid money for 35 pages = ₹ 250 × 35 = ₹ 8750

**He lost = ₹ 8750**

**(iv) If Kavimaan
helps Tamizh Nambi and they are able to produce 7 pages per day, how many days
will it take to recreate the work lost?**

Number of days it will take
to recreate the work lost = 35 ÷ 7 = 5 days

**(v) Tamizh Nambi
pays kavimaan ₹ 100 per page for his help. How much money does kavimaan
receive?**

Kavimaan receives money = ₹
35 × 100 = ₹ 3500

** **

**6. Add 2 to me. Then
multiply by 5 and subtract 10 and divide now by 4 and I will give you 15! Who
am I?**

Add 2 to me, multiply by 5 and subtract 10 and divide by 4 = 15

[ (*x*+2)5 – 10 ] / 4 =
15

5*x *+ 10 – 10 = 60

5*x* = 60

*x* *=* 60 / 5 = 12

**The number is 12.**

** **

**7. Kamatchi, a fruit
vendor sells 30 apples and 50 pomegranates. If she makes a profit of ₹ 8 per
apple and loss ₹ 5 per pomegranate, what will be her overall profit(or)loss?**

Number of apples = 30

Profit on apples = ₹ 30 × 8 = ₹240

Number of pomegranates = 50

Loss on pomegranates = ₹ 50 × 5 = ₹ 250

Loss = 250

Profit = ₹ 240

** Over all loss = ₹ 10**

** **

**8. During a drought,
the water level in a dam fell 3 inches per week for 6 consecutive weeks. What
was the change in the water level in the dam at the end of this period?**

Water level decrease per week = 3 inches

Water level decrease in 6 weeks = 3 × 6 = 18 inches

Water level decrease 18 inches in 6 weeks

** **

**9. Buddha was born
in 563 BC(BCE) and died in 483 BC(BCE). Was he alive in 500 BC(BCE)? and find
his life time. (Source: Compton’s Encylopedia)**

Buddha was bom in 563 BC (BCE) died in 483 BC (BCE)

500 BC (BCE) is in
between 563 BC and 483 BC

∴ **Yes.** He alive in 500 BC (BCE)

Life: **80 year**.

**10. A young boy has got fever.
The following chart shows how his temperature varies each day in a week. M→up
3° C, T→up 2° C, W→ Down 2° C, Th→ up 2° C, F→ Down 1° C, S→ up 2° C What was
the average daily variation in his temperature?**

(Average = Total change in temperature / Number of days)

Total change in temperature = +3 +2 –2 + 2 –1 + 2

= 9 – 3 = 6

Number of days = 6

Average = Total change in temperature / Number of days

= 6 / 6 = 1

**Average = 1**

**ANSWERS**

**Exercise 1.5 **

1. 14˚c

2. (i) −2 (ii) 0 (iii) −3 (iv) −4
(v) 1

3. (i) −2 k (ii) 318°k (iii)
−127° k (iv) 0°k

4. (i) ₹1175 (ii) ₹675 (iii) ₹325
(iv) ₹414 (v) ₹114

5. (i) 7 days (ii) 15,750 characters (iii) ₹8750 (iv) 5 days (v) ₹3,500 6. 12

7. Loss of ₹10

8. decrease of 18 inches

9. yes; 80 years

Tags : Questions with Answers, Solution | Number System | Term 1 Chapter 1 | 7th Maths , 7th Maths : Term 1 Unit 1 : Number System

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7th Maths : Term 1 Unit 1 : Number System : Exercise 1.5 | Questions with Answers, Solution | Number System | Term 1 Chapter 1 | 7th Maths

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