Q138 of 196 Page 249

About 230 billion litres of water flows through a river each day. How many litres of water flows through that river in a week? How many litres of water flows through the river in a year? Write your answer in standard notation.

Given litres of water that flow through the river in a day = 230 billion = 230, 000, 000, 000 = 230 × 109 litres


We know that 1 week = 7 days and 1 year = 365 days.


Litres of water that flow through that river in a week = 230 × 109 × 7 = 1610 × 109


In standard notation, 1610 × 109 = 1.61 × 103 × 109


We know that by properties of exponents, am × an = am + n.


1.61 × 103 × 109 = 1.61 × 103 + 9 = 1.61 × 1012


Litres of water that flow through that river in a week = 1.61 × 1012 litres


Litres of water that flow through that river in a year = 230 × 109 × 365 = 83950 × 109


In standard notation, 83950 × 109 = 8.395 × 104 × 109


We know that by properties of exponents, am × an = am + n.


8.395 × 104 × 109 = 8.395 × 104 + 9 = 8.395 × 101


Litres of water that flow through that river in a year = 8.395 × 1013 litres


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