Quantitative Aptitude - Arithmetic Ability Questions

What is the simplified value of sin2(90–θ)–[sin(90–θ)sinθ/tanθ]?

A miner sells a diamond to a trader at a profit of 40% and the trader sells it to a customer at a profit of 25%. If the customer pays Rs 56 lakhs to buy the diamond, what had it cost the miner (in Rs lakhs)?

A wholesaler sells a watch to a retailer at a gain of 35% and the retailer sells it to a customer at a loss of 25%. If the customer pays Rs 2379.375, what had it cost the wholesaler?

If x+1x=-2,then the value of x7+1x7

Seven years ago, the average age of A, B and C was 51 years. If A is 3 years older than B and B is 3 years older then C then the present ages of A, B and C are ( in year)

Mehdi can complete a work in 25 hours. If he is joined by Jahnavi who is 50% more efficient, in what time will they together finish the work?

If cot A = n/(n + 1) and cot B = 1/(2n + 1), then what is the value of cot (A + B)?

If x2 + (1/x2) = 31/9 and x > 0, then what is the value of x3 + (1/x3)?