A taxi driver filled his car petrol tank with 40 liters of petrol on Monday. The next day, he filled the tank with 50 liters of petrol. If the petrol costs` 44 per liter, how much did he spend in all on petrol?

Petrol filled on Monday = 40 liter

Petrol filled on next day = 50 liter

Total petrol filled = 90 liter [40+50=90]

Now ,

Cost of 1 Liter petrol = Rs. 44

Therefore , Cost of 90 liter petrol = 44 × 90

= 44×(100-10)

=44×100-44×10

=4400 - 440

= 3960

Hence , he spent Rs.3960 on petrol.