3. A fruit - seller purchased 50 kg of mangoes for Rs. 4500 . a) At what rate of the cost did he buy mangoes? b) Find the cost of 15 kg of the mangoes. c) In what type of proportion are the quantity and cost of the mangoes?

Find \( \lim _{x \rightarrow 1} \frac{(x+\Delta x)^{3}-x^{3}}{\Delta x} \)

b) \( -3 \sqrt[3]{2}= \)

3) \( \lim _{x \rightarrow-\infty} \frac{x^{3}+3 x-5}{10}= \)

4. Find a second-degree polynomial \[ f(x)=a x^{2}+b x+c \] such that its graph has a tangent line with slope 10 at the point \( (2,7) \) and an \( x \)-intercept at \( (1,0) \).

Justin has some 20 -cent coins and 50 -cent coins. There are 7 more 20 -cent coins than 50 -cent coins. The total value of the 50 -cent coins is \( \$ 4.90 \) more than the value of the 20 -cent coins. (a) Find the total number of 50 -cent coins. (b) Find the total value of the 20 -cent coins.