Question 3 - Figure it out - Page 86, 87 - Chapter 4 Class 7 - Another Peek beyond the Point (Ganita Prakash II)

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Question 3 Evaluate the following using the information 156 × 12 = 1872. (a) 15.6 × 1.2 = __________ (b) 187.2 ÷ 1.2 = __________ (c) 18.72 ÷ 15.6 = __________ (d) 0.156 × 0.12 = __________We use the "count the decimal places" trick here (a) 15.6 × 1.2 Since it is multiplication, we add the decimal places in both numbers We follow our steps Multiplying without decimals: 156 × 12 = 1872 Count decimal places: 1 (in 15.6) + 1 (in 1.2) = 2 total places Place the decimal 2 spots from the right: 18.72 Thus, answer is 18.72 (b) 187.2 ÷ 1.2 Since 156 × 12 = 1872 156 = 1872/12 𝟏𝟖𝟕𝟐/𝟏𝟐 = 156 Now, while dividing we follow these rules Calculate the "Gap": (Decimal places in Numerator) – (Decimal places in Denominator). The Move: If the Gap is Positive (+) → Move decimal to the Left. If the Gap is Negative (-) → Move decimal to the Right. Now, let’s do our question For 187.2 ÷ 1.2 Numerator (1) - Denominator (1)=0 Move: 0 steps. Answer: 156 Thus, answer is 156 (c) 18.72 ÷ 15.6 Since 156 × 12 = 1872 12 = 1872/156 𝟏𝟖𝟕𝟐/𝟏𝟓𝟔 = 12 Now, while dividing we follow these rules Calculate the "Gap": (Decimal places in Numerator) – (Decimal places in Denominator). The Move: If the Gap is Positive (+) → Move decimal to the Left. If the Gap is Negative (-) → Move decimal to the Right. Now, let’s do our question For 18.72 ÷ 15.6 Numerator (1) - Denominator (0)=1 Move: 1 steps. Answer: 1.2 Thus, answer is 1.2 (d) 0.156 × 0.12 Since it is multiplication, we add the decimal places in both numbers We follow our steps Multiplying without decimals: 156 × 12 = 1872 Count decimal places: 3 (in 0.156) + 2 (in 0.12) = 4 total places Place the decimal 5 spots from the right: 1872 → 001872 → 0.01872 Thus, answer is : 0.01872