Question 11 - Figure it out - Page 185 to 189 - Chapter 7 Class 7 - Finding the Unknown (Ganita Prakash II)

Transcript

Question 11 The steps to solve three equations are shown below. Identify and correct any mistakes.Mistake In the first step, the student divided the 6x and 66 by 6, but forgot to divide the 9 by 6. You cannot split the addition like that! Correction Now, 6x + 9 = 66 Putting 9 on right side, it becomes –9 6x = 66 – 9 6x = 57 Putting 6 on right side, so it divides x = 57/6 x = 𝟏𝟗/𝟐 Question 11 The steps to solve three equations are shown below. Identify and correct any mistakes.Review We review step by step Step 1: 7𝑦+12=18 (Divided entire equation by 2 . This is correct!) Step 2: 7𝑦=6 (Subtracted 12 from 18. This is correct!) Step 3: 𝑦=6/7 (Correct!) Conclusion There are no mistakes in this one. Good job to the student! Question 11 The steps to solve three equations are shown below. Identify and correct any mistakes.Mistake There are two mistakes Mistake 1: When moving the -5 to the right side, it should become +5 . The student kept it as -5 . Mistake 2: In the final step ( −5𝑥=3 ), the student wrote 𝑥=(−5)/3. To isolate 𝑥, you divide by the coefficient -5 , so it should be 3/(−5). Correction 4x – 5 = 9x + 8 Putting –5 on right side, it becomes +5 4x = 9x + 8 + 5 4x = 9x + 13 Putting 9x on left side, it becomes –9x 4x – 9x = 13 –9x + 4x = 13 x (–9 + 4) = 13 –x × (9 – 4) = 13 –x × 5 = 13 x × –5 = 13 Putting –5 on right side, so it divides Note: –5 doesn’t become + 5, because it is dividing here x = 13/(−5) x = (−𝟏𝟑)/𝟓