 Y bra statiw contains copper, zinc, and tin, with a ratio 69, 30, 1. When 345kg of copper is used in the alloy, how much zinc and tin is needed? Here's the important ratio. Copper, 69, zinc, 30, tin, 1. We need to discover the value of one part of the ratio. As 345kg of copper is 69 parts, we need to make a division calculation. 345 divided by 69 is equal to 5. Therefore, one part is equal to 5kg. To discover how many kilograms of zinc and tin are needed, we need to multiply 5kg with the correct parts of the ratio. Zinc, 30 x 5kg is equal to 150kg. Tin, 1 x 5kg is 5kg. Therefore, 150kg of zinc and 5kg of tin is needed.