Question 8 - Mind the Mistake, Mend the Mistake - Chapter 7 Class 7 - Finding the Unknown (Ganita Prakash II)

Transcript

Question 8 The following are some equations along with the steps used to solve them to find the value of the letter−number. Go through each solution and decide whether the steps are correct. If there is a mistake, describe the mistake, correct it and solve the equation.Is there a mistake? Yes What went wrong? Sign error! When multiplying -2 by -4x, the answer should be positive (+8x), because a negative times a negative is a positive. The student wrote -8x. Correct solution Now, –2(3 – 4x) = 14 Opening bracket –2 × 3 + (–2) × (–4x) = 14 –6 + 2 × 4x = 14 –6 + 8x = 14 Taking –6 on right side, it becomes +6 8x = 14 + 6 8x = 20 Taking 8 on right side, it becomes division x = 20/8 x = 𝟓/𝟐