Stuck in a problem...

Q: Evaluate $\dfrac{1}{3\times 7\times 11}+\dfrac{1}{7\times 11\times 15}+\dfrac{1}{11\times 15\times 19}\cdots ~~\text{upto 20 terms}.$

I found out the $20^{\text{th}}~\text{term}$ but not able to proceed any further...

Can anyone help?

#Algebra

Easy Math Editor

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`2 \times 3`	$2 \times 3$
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`a_{i-1}`	$a_{i-1}$
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Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$