The presence of hardness in excess of permissible limit causes

The alkalinity and the hardness of a water sample are 250 mg/L and 350 mg/L as $$CaCo_3$$, respectively. The water has

The plan of a map was photo copied to a reduced size such that a line originally 100mm, measures 90mm. The original scale of the plan was 1:1000. The revised scale is

The plan of a survey plotted to a scale of 10m to 1cm is reduced in such a way that a line originally 10cm long now measures 9cm. the area of the reduced plan is measured as 81cm2. the actual (m2) of the survey is