Question
The average of 10 numbers is 21.6. The average of the
first four numbers is 17.5, and the average of the last three numbers is 24. The fifth number is 6 less than the sixth number, which itself is 8 less than the seventh number. What is the average of the fifth and sixth numbers?Solution
Sum of fifth, sixth and seventh numbers = 21.6 X 10 - 17.5 X 4 - 24 X 3= 216 - 70 - 72 = 74Let the seventh number be 'p'.Sixth number = p - 8Fifth number = p - 8 - 6 = p - 14So, p + p - 8 + p - 14 = 74Or, 3p - 22 = 74Or, 3p = 96Or, 'p' = 32Required average = (p - 8 + p - 14) ÷ 2 = p - 11 = 32 - 11 = 21
Which of the following statement is/are true?
I. Metal oxides are acidic in nature
II. Non-metallic oxides are basic in nature
Acid rain is caused due to pollution of the atmosphere by:
What is heavy water?
The motion of an object under free fall is an example of which of the following?
Which radioactive element is used in heart pacemakers?
A mixture of carbon monoxide and hydrogen is known as ______
Which of the following alkali metals has the highest specific heat?
What changes will happen to a bowl of ice and water kept at exactly zero degree Celsius?
Bases react with acids to form ________.
Which is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe’s elemental mass?
Relevant for Exams:
