How did Sparta keep their slaves from revolting

The number of helots in relation to Spartan citizens varied throughout the history of the Spartan state; according to Herodotus, there were seven helots for each Spartan at the time of the Battle of Plataea in 479 BC. Thus the need to keep helot population in check and prevent rebellion was one of the main concerns of the Spartans. Helots were ritually mistreated, humiliated and even slaughtered: every autumn the Spartans would declare war on the helots so they could be killed by a member of the Crypteia without fear of religious repercussion. Uprisings and attempts to improve the lot of the helots did occur, such as the Conspiracy of Cinadon.

Explanation:

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d. it adversely affected american productivity

the correct answer is:   "   3.6 % " .

          →   the unemployment rate is:   " 3.6 % " .

explanation:

to calculate the "unemployment rate" :

the "unemployment rate"   =

  [# of people unemployed] /   [working age population]   * 100 %   ;

                =   [9 million] / [250 million]     *   100 % ;

    →     note:   the units of "million" cancel out;

                    since:   " {million} / {million} = 1 " ;

                =   (9 / 250)   * 100 %   ;

                = 0.036 * 100 % ;

                =   3.6 %

answer:   the unemployment rate is:   " 3.6 % " .