. aritmetičkom nizu je \( a_{3}=-23.6, a_{17}=-19.4 \). Je li broj 0.1 član tog niza i ako jest, koji je po redu to član u nizu?

15. \( 1-(2-3)+8= \) 16. \( 12-4(7-2)= \) 17. \( 18 \div(6+3)-12= \)

Simplify these fractions. \( \begin{array}{ll}\text { (15) } \frac{16}{20}= & \text { (18) } \frac{9}{81}= \\ \text { (16) } \frac{4}{128}= & \text { (19) } \frac{16}{20}= \\ \text { (17) } \frac{10}{15}= & \text { (20) } \frac{30}{445}=\end{array} \)

(a) What was the TOTAL cost of the stamps? (b) She had to post a parcel and the total cost of postage was \( \$ 25.70 \). What stamps can she select from the collection, to make up this amount if she must use (i) as many \( \$ 4.00 \) stamps as possible? (ii) all her \( \$ 1.00 \) stamps? 3 marks) (c) 2 marks) (i) What is the LARGEST number of stamps that she can use from the collection (ii) List the selection of stamps she can use. 3 marks)

If the numerical value of 5, 5.0, and 5.00 are the same, why is it necessary to include the zeros in measurements?

18. \( 10^{2}+3^{3}-2 \times 3= \) 19. \( 4^{2}+(7+2) \div 3= \) 20. \( 7 \times 4-9 \div 3= \)