Live practice

\(t(0)=32\). \[\begin{aligned}t(28) &= 9(28)/5+32\\&= 82.4\end{aligned}\]. \[\begin{aligned}t(-10) &= -18+32\\&= 14\end{aligned}\].

For \(t(C)=212\):

Every element of \(A\) already belongs to \(B\). Therefore adding the elements of \(A\) introduces nothing new to \(B\), so \(A\cup B=B\).

\[\begin{aligned}P &= VI\\&= 220(5)\\&= 1100\end{aligned}\] W = 1.10 kW.

Form a sharp image of a candle on a screen with an uncovered lens, then cover the upper half without moving lens or screen. The complete image remains at the same position and size but becomes dimmer. Every small region of a lens receives rays from every object point and can form the whole image; covering half merely reduces transmitted light.

Contraception allows spacing and limiting of children, avoids unintended pregnancy, protects maternal and child health and supports family planning according to resources. Condoms also reduce transmission of STIs. Medical advice helps select a safe, effective and reversible or permanent method.

Many organs work simultaneously and must respond appropriately to changing internal and external conditions. Control systems receive information, integrate it and coordinate effectors so that responses are timely and compatible. This maintains homeostasis, avoids conflicting actions and improves survival.

Xylem carries water and dissolved mineral ions from roots to aerial parts. Food is transported by phloem.

Hard water contains \(\ce{Ca^{2+}}\) and \(\ce{Mg^{2+}}\). These ions react with soluble sodium or potassium salts of fatty acids and form insoluble calcium or magnesium soap:

The curdy precipitate is scum. It consumes soap and prevents easy lather formation.

The impure metal M is made the anode so that it dissolves. A thin sheet of pure M is the cathode, where metal ions gain electrons and deposit. The electrolyte is a soluble salt solution of M. Soluble impurities remain in solution; insoluble impurities settle as anode mud.

An antacid is a mild base that neutralises excess hydrochloric acid in the stomach and provides relief from acidity.