Q6
3 marks
Arithmetic Sequences and Series
Summation of Derived Sequence from AP
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Let $l _ { 1 } , l _ { 2 } , \ldots , l _ { 100 }$ be consecutive terms of an arithmetic progression with common difference $d _ { 1 }$, and let $w _ { 1 } , w _ { 2 } , \ldots , w _ { 100 }$ be consecutive terms of another arithmetic progression with common difference $d _ { 2 }$, where $d _ { 1 } d _ { 2 } = 10$. For each $i = 1,2 , \ldots , 100$, let $R _ { i }$ be a rectangle with length $l _ { i }$, width $w _ { i }$ and area $A _ { i }$. If $A _ { 51 } - A _ { 50 } = 1000$, then the value of $A _ { 100 } - A _ { 90 }$ is $\_\_\_\_$.