Question

下式的值是多少？

$\tiny 2(81 + 83 + 85 + 87 + 89 + 91 + 93 + 95 + 97 + 99)?$

What is the value of

$\tiny 2(81 + 83 + 85 + 87 + 89 + 91 + 93 + 95 + 97 + 99)?$

$1600$

$1650$

$1700$

$1750$

$1800$

这十个等间隔数的平均数是 $90$ ，所以它们的和是 $10 \times 90 = 900$ 。

加倍后得到 $2 \times 900 = 1800$ 。

所以正确答案是 E。

The ten evenly spaced numbers have average $90,$ so their sum is $10 \times 90 = 900.$

Doubling gives $2 \times 900 = 1800.$

Thus, the correct answer is E .