Before starting an exercise, memorize and understand the logic behind the formulas highlighted in the chapter summaries.
17. $3x + 6 + 10x - 5 - 4x + 12 = 9x + 13$. Put $x=2$: $9(2) + 13 = 18 + 13 = 31$. 18. Correct: $4 \times 5 = 20$. Incorrect: $5 \times (-2) = -10$. Total = $20 + (-10) = 10$ marks. 19. Mean = Sum/11 = 324/11 = 29.45. Mode = 15. Median = Middle value (arrange first) = 15. 20. Construction steps: Draw base QR=7cm. From Q, cut arc 6cm. From R, cut arc 5cm. Intersection is P. Join lines. 21. Supplement of $45^\circ = 180 - 45 = 135^\circ$. Angle $y = 135^\circ$ (Linear Pair). 22. $4y$. 23. $x = 0.333... \Rightarrow 10x = 3.33... \Rightarrow 9x = 3 \Rightarrow x = 1/3$. 24. Ext Angle = Sum of opposite interior. $110 = 60 + x \Rightarrow x = 50^\circ$. rd sharma class 7 maths
Let’s be honest. For most 12- and 13-year-olds, the word mathematics triggers one of two reactions: a quiet hum of confidence or a cold sweat. If you fall into the second category, or even if you’re in the first and want to stay there, there is one name that has dominated Indian middle school math for decades: . Before starting an exercise, memorize and understand the