Answer:
252
Step-by-step explanation:
9 x 28 = (9 x 20) + (9 x 8)
9 x 20 = 180
9 x 8 = 72
180 + 72 = 252
9 x 28 = 252
(hope this helps can I pls have brainlist (crown) ☺️)
Answer:
-159
Step-by-step explanation:
<span><span>220<span> cm2</span>/s </span>
EXPLINATION</span>
L length of rectangel (cm)
W width of rectangel(cm)
A area of rectangel (cm²)
T time (s)
we are told that:
d1\dt=8cm\s(const),and dw\dt =3cm\s(const)
the area of the rectangel is
A=LW
Differentiating wrt t (using the product rule) we get;
<span><span><span>dA</span><span>dt</span></span>=<span>(l)</span><span>(<span><span>dw</span><span>dt</span></span>)</span>+<span>(<span><span>dl</span><span>dt</span></span>)</span><span>(w)</span></span>
∴<span><span>dA</span><span>dt</span></span>=3l+8w
So when <span>l=20</span><span> and </span><span>w=10⇒</span>
<span> <span><span>dA</span><span>dt</span></span>=3⋅20+8⋅20</span>
<span>∴<span><span>dA</span><span>dt</span></span>=60+160</span>
<span>∴<span><span>dA</span><span>dt</span></span>=220<span> cm2</span>/<span>s</span></span>
