Directions (Set of 5 questions): What approximate value should come in place of the question marks(?) in the following questions? (Note : you are not expected to calculate the exact value.)
$2201.13~\times 4.35-~{{?}^{2}}\times 123.75=-15500$
Solution
$2201.13~\times 4.35-~{{?}^{2}}\times 123.75=-15500$
${{?}^{2}}\times 123.75\approx 2201~\times 4+15500$
${{?}^{2}}\times 124=8804+15500$
${{?}^{2}}\times 124=24304$
${{?}^{2}}=\frac{24304}{124}=196$
$?=~\sqrt{196}=14$