Question 628177
{{{ 10/A = A/4.9 }}}
Multiply both sides by {{{ 4.9A }}}
{{{ 4.9A*(10/A) = 4.9A*(A/4.9) }}}
On the left side, the {{{A}}}'s cancel
On the right side, the {{{ 4.9 }}}'s cancel
{{{ 4.9*10 = A^2 }}}
{{{ 49 = A^2 }}}
Take the square root of both sides
{{{ A = 7 }}}
and, taking the negative square root of {{{A^2}}}
{{{ A = -7 }}}
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check the answers:
{{{ 10/A = A/4.9 }}}
{{{ A = -7 }}}
{{{ 10/(-7) = -7/4.9 }}}
{{{ -1.4286 = -1.4286 }}}
OK
{{{ A = 7 }}} will check OK too