# CBSE Class 10-Mathematics: Chapter –4 Quadratic Equations Part 24

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**Question 7:**

A plane left minutes later than the schedule time and in order to reach its destination away in time it has to increase its speed by from its usual speed. Find its usual speed.

**Answer:**

Let usual speed

New speed

Total distance

Time taken by usual speed

Time taken by new speed

According to question,

Therefore, usual speed is is neglected.

**Question 8:**

A motorboat, whose speed is in still water, goes downstream and comes back in a total time of minutes, find the speed of the stream.

**Answer:**

Speed of motorboat in still water

Speed of stream =

Speed in downward direction

Speed in downward direction

According to question,

Speed of stream

**Question 9:**

A swimming pool is filled with three pipes with uniform flow. The first two pipes operating simultaneously fill the pool in the same time during which the pool is the same time during which the pool is filled by the third pipe alone. The second pipe fills the pool five hours faster than the first pipe and four hours slower than the third pipe. Find the time required by each pipe to fill the pool separately.

**Answer:**

Let be the number of hours required by the second pipe alone to till the pool and first pipe hour while third pipe hour

**Question 10:**

A two-digit number is such that the product of its digits is 18. When 63 is subtracted from the number the digit interchange their places. Find the number.

**Answer:**

Let digit on unit’s place

Digit on ten’s place

Number

According to question,

Number