1. INCREASE AND DECREASE IN A GIVEN RATIO

2. If you want to increase $85 in the ratio 7 : 5 there are two possible methods. Method 1 5 parts = $85 1 part = $85 ÷ 5 = $17 7 parts = 7 × $17 = $119 So answer is $119 Method 2

3. Example 1Decrease 120 kg in the ratio 19 : 20. Method 1 20 parts = 120 kg 1 part = 120 kg ÷ 20 = 6 kg 19 parts = 19 × 6 kg = 114 kg So answer is 114 kg Method 2

4. Example A photo measures 20 cm by 15 cm. The photo is enlarged in the ratio 8 : 5. a Calculate the measurements of the enlarged photo. b Write down and simplify the ratio area of enlarged photo : area of original photo 20 cm 15 cm a b area of original photo = area of enlarged photo = area of enlarged photo : area of original photo =768 : 300 =64 : 25 15 x 20 =300 cm 2 32 x 24 =768 cm 2 2 note: 8 2 : 5 2 = 64 : 25

5. a Calculate the measurements of the large box. b Write down and simplify the ratio volume of large box : volume of regular box washing powder LARGE Example 3 washing powder REGULAR 20 cm 8 cm 24 cm a b volume of regular box = volume of large box = volume of large box : volume of regular box =7500 : 3840 =125 : 64 20 x 8 x 24 =3840 cm 3 25 x 10 x 30 =7500 cm 3 A company sells regular size boxes of washing powder. They decide to make a large size box by increasing the dimensions in the ratio 5 : 4. note: 5 3 : 4 3 = 125 : 64

6. Example 4This tablecloth shrinks when it is washed. The length decreases in the ratio 74 : 75. The width decreases in the ratio 89 : 90. a Calculate the measurements of the tablecloth after it is washed. b Write down and simplify the ratio area of tablecloth before washing : area of tablecloth after washing a b area before washing = area after washing = area before washing : area after washing =40 500 : 39 516 = 3375 : 3293 180 x 225 =40 500 cm 2 222 x 178 =39 516 cm 2 length = 225 cm width = 180 cm