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4.Average
hard
Average rainfall on Monday, Tuesday, Wednesday and Thursday is $420.5\, cm$ and average on Tuesday, Wednesday, Thursday and Friday is $440.5\, cm .$ If the ratio of rainfall for Monday and Friday is $20: 21,$ find the rainfall in $cm$ on Monday and Friday.
A
$1800,1890$
B
$1600,1680$
C
$1700,1470$
D
$1682,1762$
Solution
$M+T+W+T h=4 \times 420.5=1682 cm$ ….$(1)$
$T+W+ Th +F=4 \times 440.5=1762 cm$ ….$(2)$
By equation $(2)-$equation $(1),$ we have
$F-M=1762-1682=80$
Let the rainfall for Monday and Friday be $20 x$ and $21 x$ cm respectively. Now, according to the question,
$21 x-20 x=80$
$\Rightarrow x=80$
$\therefore$ Monday $\Rightarrow 80 \times 20=1600 cm$
$\therefore$ Friday $\Rightarrow 21 \times 80=1680 cm$
Std 13
Quantitative Aptitude
