Question

Write two situations for the following where brackets would be necessary.
a. 7 × (8 − 3)
b. (7 + 2) × (10 − 3)

Answer 1

Answer:

Solution

\Large{\underline{\mathfrak{\bf{Given}}}}

Given

Distance of object from concave mirror (U) = -10 cm

Radius of curvature of concave mirror ( R ) = -8 cm = 2F

So, F = -8/2 = -4 cm

\Large{\underline{\mathfrak{\bf{Find}}}}

Find

Distance of image (V) .

\Large{\underline{\underline{\mathfrak{\bf{Explanation}}}}}

Explanation

\Large{\underline{\mathfrak{\bf{Using\:mirror\:formula}}}}

Usingmirrorformula

\red{\boxed{\sf{\orange{\:\dfrac{1}{F}\:=\:\dfrac{1}{U}\:+\:\dfrac{1}{V}}}}}

F

1

=

U

1

+

V

1

Substitute value of U and F in above equation ,

\begin{gathered}:\implies\sf{\:\dfrac{1}{V}\:+\:\dfrac{1}{-10}\:=\:\dfrac{1}{-4}} \\ \\ :\implies\sf{\:\dfrac{1}{V}\:=\:-\:\dfrac{1}{4}\:+\:\dfrac{1}{10}} \\ \\ :\implies\sf{\:\dfrac{1}{V}\:=\:\dfrac{-10+4}{40}} \\ \\ :\implies\sf{\:\dfrac{1}{V}\:=\:\dfrac{-14}{40}} \\ \\ :\implies\sf{\:V\:=\:\dfrac{-40}{14}} \\ \\ :\implies\sf{\red{\:V\:=\:\dfrac{-20}{7}\:cm}}\end{gathered}

:⟹

V

1

+

−10

1

=

−4

1

:⟹

V

1

=−

4

1

+

10

1

:⟹

V

1

=

40

−10+4

:⟹

V

1

=

40

−14

:⟹V=

14

−40

:⟹V=

7

−20

cm

\Large{\underline{\mathfrak{\bf{Thus}}}}

Thus

Distance of image (V ) = -20/7 cm

When, the image distance is negative , the image is behind the mirror .

1. So, the image is virtual and upright.

Answer 2

Answer:

$holr</p><p></p><p></p><p></p><p></p><p></p><p>Write five situations for the following where brackets would be necessary. (a) 7(8-3) b) (7 +2) (10-3)</p><p></p><p>English</p><p></p><p></p><p></p><p> </p><p></p><p></p><p></p><p></p><p></p><p>1 Answers</p><p></p><p></p><p></p><p>Shambhu Shere</p><p></p><p>Grade 10</p><p></p><p></p><p></p><p></p><p>a) 7(8-3) </p><p>[ when we will open bracket 8 and 3 will be multiplied by 7]</p><p></p><p>= (7×8) - ( 7×3)</p><p></p><p>= 56 - 21</p><p></p><p>= 35 </p><p></p><p>Direct Method , solve the bracket first -</p><p></p><p>7(8-3)</p><p>= 7×5 </p><p>= 35</p><p></p><p>b) (7+2)(10-3)</p><p>[we will open one of the brackets]</p><p></p><p>7(10-3) + 2(10-3)</p><p></p><p>= {(7×10) - (7×3)} + {(2×10 - 2×3)}</p><p></p><p>= {70-21} + {20-6}</p><p></p><p>= 49 + 14</p><p></p><p>= 63</p><p></p><p>Direct Method , solve the brackets -</p><p></p><p>(7+2) (10-3)</p><p>= 9 × 7</p><p>= 63</p><p></p><p>$