If a ∶ b ∶ c ∶ d = √4∶√3∶√2∶√1, then what is the value of $$\frac{-a^2 + b^2 + c^2 + d^2}{a^2 - b^2 + c^2 - d^2}$$ ?​

Find the value of x in the proportion 69 : 23 :: 63 : x.

The ratio of the incomes of A and B is 3 : 5 and the ratio of their expenditures is 2: 3. If the income of A is equal to 6/7 of the expenditure of B, then the ratio of the savings of A and B is :

The ratio of number of boys and girls in a school of 3528 students is 5:4. How many more girls should be admitted in the school to make this ratio 1:1?

If the third proportional of 28 and 70 be x, then what is the value of x?

The cost of 40 packets of 12 pens is ₹1680. The cost of 30 packets each containing 9 pens is

The first, second and fourth numbers in a proportion are 31, 12 and 156 respectively.

The mean proportional between 25 and a number N is two times the mean proportional between 15 and 35.

Compare the ratios 12 : 13, 7 : 8, 9 : 10, and 5 : 6. Which one is greater than 0.9 but smaller than 0.95?