Question

answer this question first ​

Answer 1

Solution :-

Let

→ Ball = x

→ Cube = y .

Given :-

→ (x + y) = 100

→ (x - y) = 80

→ x * y = ?

we know That,

→ (x + y)² = (x - y)² + 4xy

Putting Values we get,

→ (100)² = (80)² + 4xy

→ 4xy = (100)² - (80)²

Now, using (a + b)(a - b) = a² - b²

→ 4xy = (100 + 80)(100 - 80)

→ 4xy = 180 * 20

→ xy = 180 * 5

→ xy = 900 (Ans.)

Hence, Ball × Cube is Equal to 900.

[ Ball = 90, Cube = 10 ].

Answer 2

Solution :-

Let

• Ball = x
• Cube = y .

Given :

• (x + y) = 100

• (x - y) = 80

To Find :

• x × y =??

We know that

• $\sf {{(x + y)}^{2} = {(x - y)}^{2} + 4xy}$

By substituting values we get :

$\sf {:\implies{(100)^2 = (80)^2+ 4xy}}\\ \\\sf {:\implies{4xy = (100)^2- (80)^2}}$

We also know that

• $\sf {(a + b)(a - b) = a^2 - b^2}$

$\bf{Now,\: by \:using\: (a + b)(a - b) = a^2 - b^2}$

$\sf {:\implies{4xy = (100 + 80)(100 - 80)}} \\\\ \sf {:\implies {4xy = 180 \times 20}}\\\\ \sf {:\implies {xy = \dfrac {180 \times 20}{4}}}\\\\ :\implies{\boxed{\tt{xy = 900 }}}$

$\bf {\therefore {Ball × Cube =900.}}$

$\rule {307}{2}$