8th Class Mathematics Linear Equations in One Variable

  • question_answer 1)
                    Solve the following equations: 1.            \[x-2=7\] 2.            \[y+3=10\] 3.            \[6=z+2\] 4.            \[\frac{3}{7}\,+x=\frac{17}{7}\] 5.            \[6x=12\] 6.            \[\frac{t}{5}=10\] 7.            \[\frac{2x}{3}=18\] 8.            \[1.6=\frac{y}{1.5}\] 9.            \[7x-9=16\] 10.          \[14y-8=13\] 11.          \[17+6p=9\] 12.          \[\frac{x}{3}+1=\frac{7}{15}\]

    Answer:

                    1. \[x-2=7\] We have \[x-2=7\] \[\Rightarrow \]               \[x=7+2\]                                            |Transposing ? 2  to R.H.S. \[\Rightarrow \]               \[x=9\] This is the required solution. Check: L.H.S. \[=x-2=9-2\] = 7 = R.H.S. (as required) 2.            \[y+3=10\] We have \[y+3=10\] \[\Rightarrow \]               \[y=10-3\]                                           | Transposing 3 to R.H.S. \[\Rightarrow \]               \[y=7\] This is the required solution. Check: L.H.S. \[=y+3=7+3=10\] = R.H.S. (as required) 3.            \[6=z+2\] We have  \[6=z+2\] \[\Rightarrow \]         \[62=z\]                                      | Transposing 2 to L.H.S. \[\Rightarrow \]               \[4=z\] \[\Rightarrow \]               \[z=4\] This is the required solution. Check: R.H.S. \[=z+2=4+2=6\] = L.H.S. (as required) 4.            \[\frac{3}{7}+x=\frac{17}{7}\] We have \[\frac{3}{7}+x=\frac{17}{7}\] \[\Rightarrow \]               \[x=\frac{17}{7}-\frac{3}{7}\]                                      | Transposing \[\frac{3}{7}\] to R.H.S. \[\Rightarrow \]               \[x=\frac{17-3}{7}\] \[\Rightarrow \]               \[x=\frac{14}{7}=2\] This is the required solution. Check: L.H.S. \[=\frac{3}{7}+x=\frac{3}{7}+2\]                 \[=\frac{17}{7}\,=\] R.H.S. (as required) 5.            \[6x=12\] We have \[6x=12\] \[\Rightarrow \]               \[x=\frac{12}{6}=2\] This is the required solution. Check: L.H.S.\[=6x=6\times 2=12\] = R.H.S.      (as required) 6.            \[\frac{t}{5}=10\] We have   \[\frac{t}{5}=10\] \[\Rightarrow \]               \[t=10\times 5=50\]                        | Multiplying both sides by 5 This is the required solution. Check: L.H.S. \[=\frac{t}{5}=\frac{50}{5}=10\] = R.H.S.                (as required) 7.            \[\frac{2x}{3}=18\] We have \[\frac{2x}{3}=18\] \[\Rightarrow \]               \[2x=18\times 3\]            |Multiplying both sides by 3 \[\Rightarrow \]               \[2x=54\] \[\Rightarrow \]               \[x=\frac{54}{2}=27\] Thus is the required solution.                 Check: L.H.S. \[=\frac{2x}{3}=\frac{2\times 27}{3}=18\] = R.H.S. (as required) 8.            \[1.6=\frac{y}{1.5}\]                 We have \[1.6=\frac{y}{1.5}\] \[\Rightarrow \]               \[1.6\times 1.5=y\]         | Multiplying both sides by 1.5 \[\Rightarrow \]               \[2.4=y\] \[\Rightarrow \]               \[y=2.4\] This is the required solution. Check: RHS \[=\frac{y}{1.5}=\frac{2.4}{1.5}=1.6\] = LHS    (as required) 9.            \[7x-9=16\] We have \[7x-9=16\] \[\Rightarrow \]               \[7x=16+9\]                        |Transposing ? 9 to RHS \[\Rightarrow \]               \[7x=25\] \[\Rightarrow \]               \[x=\frac{25}{7}\]                            | Dividing both sides by 7 This is the required solution. Checks: LHS \[=7x-9=7\times \frac{25}{7}-9\] \[=25-9=16=\text{RHS}\]              (as required) 10.          \[14y-8=13\]                 We have \[14y-8=13\] \[\Rightarrow \]               \[14y=13+8\]                     | Transposing ? 8 to RHS \[\Rightarrow \]               \[14y=21\] \[\Rightarrow \]               \[y=\frac{21}{24}\]                          | Dividing both sides by 14 \[\Rightarrow \]               \[y=\frac{21\div 7}{14\div 7}=\frac{3}{2}\] This is the required solution. Check: LHS \[=14y-8=14\left( \frac{3}{2} \right)-8\] \[=21-8=13\]= RHS (as required) 11.          \[17+6p=9\] We have \[17+6p=9\] \[\Rightarrow \]        \[6p=9-17\]                                | Transposing 17 to RHS \[\Rightarrow \]         \[6p=-8\] \[\Rightarrow \]               \[p=\frac{-8}{6}\]                             | Dividing both sides by 6 \[\Rightarrow \]               \[p=\frac{-8\div 2}{6\div 2}\] \[\Rightarrow \]               \[p=\frac{-4}{3}\] This is the required solution. Check: LHS \[=17+6p\] \[=17+6\left( \frac{-4}{3} \right)\] \[=17-8=9\]                 = RHS (as required) 12.          \[\frac{x}{3}+1=\frac{7}{15}\]                 We have \[\frac{x}{3}+1=\frac{7}{15}\] \[\Rightarrow \]               \[\frac{x}{3}=\frac{7}{15}-1\]                      |Transposing 1 to RHS \[\Rightarrow \]               \[\frac{x}{3}=\frac{7-15}{15}\] \[\Rightarrow \]               \[\frac{x}{3}=\frac{-8}{15}\] \[\Rightarrow \]               \[x=\left( -\frac{8}{15} \right)\times 3\]                | Multiplying both sides by 3       \[\Rightarrow \]               \[x=\frac{-8}{5}\] This is the required solution. Check: LHS \[=\frac{x}{3}+1\]                 \[=\frac{1}{3}\left( \frac{-8}{5} \right)+1\] \[=\frac{-8}{15}+1\] \[=\frac{-8+15}{15}=\frac{7}{15}\] = RHS                    (as required)


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