Kerala Syllabus Class 7 Mathematics - Unit 7 Shorthand Math - Questions and Answers | Teaching Manual 

Questions and Answers for Class 7 Mathematics - Unit 7 Shorthand Math - Study Notes | Text Books Solution STD 7 - Maths: Unit 7 Shorthand Math - Questions and Answers | ഗണിതം - കണക്കിലെ ചുരുക്കെഴുത്ത് - ചോദ്യോത്തരങ്ങൾ 

ഏഴാം ക്ലാസ്സ്‌  Mathematics - Unit 7 Shorthand Math എന്ന പാഠം ആസ്പദമാക്കി തയ്യാറാക്കിയ ചോദ്യോത്തരങ്ങള്‍. ഈ അധ്യായത്തിന്റെ Teachers Handbook, Teaching Manual എന്നിവ ഡൗൺലോഡ് ചെയ്യാനുള്ള ലിങ്ക് ചോദ്യോത്തരങ്ങളുടെ അവസാനം നൽകിയിട്ടുണ്ട്.

Kerala Syllabus STD 7 Maths: Unit 7 Shorthand Math - Textbook Solutions

♦ Textbook Activities (Textbook Page No: 96)
(I) Now, can't you write the following statements using the language of
algebra?

(1) Zero added to any number gives the same number.
Answer: For any number '𝑥' ; 𝑥 + 0 = 𝑥

(2)  Zero subtracted from any number gives the same number.
Answer: For any number '𝑥' ; 𝑥 - 0 = 𝑥

(3) Any number subtracted from the same number gives zero.
Answer: For any number '𝑥' ; 𝑥 - 𝑥 = 0

(4)  Any number multiplied by zero gives zero.
Answer: For any number '𝑥' ; 𝑥 x 0 = 0

(5) Any number divided by the same number gives 1.
Answer: For any number '𝑥' ; ˣ⁄ₓ = 1

(6)  Twice a number added to the number makes three times the number.
Answer: For any number '𝑥' ; 𝑥 + 2𝑥 = 3𝑥

(7) Twice a number subtracted from thrice the number gives the number.
Answer: For any number '𝑥' ; 3𝑥 - 2𝑥 = 𝑥

(8) A number added to a number, and then the added number subtracted gives the original number.
Answer: For any two numbers '𝑥' and 'y', 𝑥 + y - y = 𝑥

♦ Textbook Activities (Textbook Page No: 98)
Now do the following problems mentally:
1. (i)  49 + 125 + 75
49 + (125 + 75) = 49 + 200 = 249

(ii) 3½ + 8¾ + ¼
8¾ + ¼ = 9; 3½ + 9 = 12½

(iii) 15.5 + 0.25 + 0.75
15.5 + (0.25 + 0.75) = 15.5 + 1 = 16.5

(iv) 38 + 27
38 + 27 can be written as 38 + 2 + 25
38 + 27 = (38 + 2) + 25 = 40 + 25 = 65

(v) 136 + 64
136 + 64 can be written as 136 + 4 + 60
136 + 64 = (136 + 4) + 60 = 140 + 60 = 200

(2) (i) (135 - 73) - 27
Answer: (135 - 73) - 27 = 135 - (73 + 27) = 135 - 100 = 35

(ii) (37 - 1½) - ½
Answer: (37 - 1½) - ½ = 37 - (1½ + ½) = 37 - 2 = 35

(iii) (298 - 4.5) - 3.5
(298 - 4.5) - 3.5 = 298 - (4.5 + 3.5) = 298 - 8 = 290

(iv) 78 - 29
78 - 29 = 78 - 28 - 1 
78 - 28 = 50
50 - 1 = 49

(v) 140 - 51
140 - 51 - 11
100 - 11 = 89
♦ Textbook Activities (Textbook Page No: 99)
Now you can try to calculate these mentally:
(i)  (136 + 29) - 19
(136 + 29) - 19 = 136 + (29 - 19) = 136 + 10 = 146
(Subtract 19 from 29, we get 10, and add it to 136)

(ii) (3½ + 5¾) - 2¼
3½ = ⁷⁄₂ ; 5¾ = ²³⁄₄; 2¼ = ⁹⁄₄
∴ (3½ + 5¾) - 2¼ = (⁷⁄₂ + ²³⁄₄) - ⁹⁄₄ = ⁷⁄₂ + (²³⁄₄ - ⁹⁄₄)
                          = ⁷⁄₂ + ¹⁴⁄₄ = ⁷⁄₂ + ⁷⁄₂ = 7

(iii) (298 + 14.5) - 12.5
(298 + 14.5) - 12.5 = 298 + (14.5 - 12.5)
= 298 + 2 = 300 (Subtract 12.5 from 14.5 to get 2)

(iv) 23 + (35 -18)
Add (35 -18) = 17 to 23 to get 40
(23 + (35 - 18) = 23 + 17 = 40)
Subtract 18 from 23 + 35 = 58, to get 40
((23 + 35) - 18 = 40)

(v) 65 + 98
65 + 98 = 65 + 100 - 2 = (65 + 100) - 2 = 163

♦ Textbook Activities (Textbook Page No: 101)
Try to do these problems in head:
 (i) (135 - 73) + 23
(135 - 73) + 23 = 135 - (73 - 23) = 135 - 50 = 85

(ii) (38 - 8½) + ½
(38 - 8½) + ½ = 38 - (8½ - ½) = 38 - 8 = 30

(iii) (19 - 6.5) + 2.5
(19 - 6.5) + 2.5 = 19 - (6.5 + 2.5) = 19 - 4 = 15

(iv) 135 - (35 - 18)
135 - (35 - 18) = (135 - 35) + 18 = 100 + 18 = 118

(v) 240 - (40 - 13)
240 - (40 - 13) = (240 - 40) + 13 = 200 + 13 = 213
♦ Textbook Activities (Textbook Page No: 102)
Now try to do these mentally:
(i) 103 × 15
103 × 15 = (100 + 3) x 15
              = (100 x 15) + (3 x 15)
              = 1500 + 45 = 1545

(ii) 98 × 25
98 × 25 = (100 - 2) x 25
            = (1000 x 25) - (2 x 25)
            = 2500 - 50 = 2450

(iii) (63 × 12) + (37 × 12)
(63 × 12) + (37 × 12) = (63 + 37) x 12 = 100 x 12 = 1200

(iv) (65 × 11) - (55 × 11)
(65 × 11) - (55 × 11) = (65 - 55) x 11 = 10 x 11 = 110

(v) (15 x ¾) + (5 x ¾)
(15 x ¾) + (5 x ¾) = (15 + 5) x ¾ = 20 x ¾ = 15

(vi) (5½ x 23) - (4½ x 23)
(5½ x 23) - (4½ x 23) = (5½ - 4½) x 23 = 1 x 23 = 23