5452 Shares

Topic: Can you help me with my math?**Question:**
Old silver coins contain 90% silver. Silver solder contains 63% silver. If you wanted to make 200 kilograms of an alloy containing 81% silver, how many kilograms of old coins and how many kilograms of silver solder could you melt together to do this?

June 16, 2019 / By Charissa

Ahhh, ye olde % problem that most teachers are unable to clearly explain. Call x the kg's of old coins you need and y the kg's of silver solder. Then the total kg's must add up to 200, so the first equation is x+y = 200 Next, there are x*0.90 kg of silver in the old coins and y*0.63 kg of silver in the silver solder. So, the total amount of silver is 0.90x +0.63y. This must be 81% of the total mass, i.e. 0.81*200. So, your second equation is 0.9x+0.63y = 162 You solve for x and y. Simple enough?

👍 266 | 👎 9

Did you like the answer? If you have tried working it out yourself but still can't find the answer the get an app called neocal. It costs money but you can use it for so many different things that its worth it in the long run. It has 5 different pages and they are all for working out different things. Its like a very advanced calculator. It's on android and i think its on ios aswell but im not sure

Let silver = x and silver solder =y since x+y must =200, therefore x =200 -y .90(x) +.63y =.81(200) .90(200 -y) +.63y =.81(200) lets rid fraction by multiplying all by 100 90(200-y) +63y = 81(200) 18000-90y +63y = 16200 1800 = 27y 66.67 =y =kg of silver solder coins 200 -66.67 = x =133.33 = kg of 90% silver coins

👍 110 | 👎 2

x := the weight of silver coins y := the weight of silver solder x+y = 200 90x+63y = 200*81 multiply the first equation by 63 and subtract it from the second 27x = 200*(81-63) = 3600 x = 133.3 kg y = 66.7 kg

👍 102 | 👎 -5

Let x kg of coins be mixed with y kg of solder. x+y=200 In x kg coins, solver=9x/10 kg. In y kg solder, silver=63/100 kg. 9x/10+63x/100=81/100(x+y) or, (90x+63y)/100=81/100*200 or, (90x+63y)/100=162 or, 90x+63y=16200 90x+90y=18000 27y=1800 y=200/3=66.66 x=200-200/3=(600-200)/3=400/3=133.33 133.33 kg of coins are to be mixed with 66.66 kg of solder. Hope this helps!!!

👍 94 | 👎 -12

Use trigonometry (kinda means triangle measuring). Consider that the building and the shadow make a right angle (assuming the ground is horizontal. The angle you want is arctan(230/100). Arctan means inverse tan or 'tan^-1'

If you have your own answer to the question Can you help me with my math?, then you can write your own version, using the form below for an extended answer.
/**
* RECOMMENDED CONFIGURATION VARIABLES: EDIT AND UNCOMMENT THE SECTION BELOW TO INSERT DYNAMIC VALUES FROM YOUR PLATFORM OR CMS.
* LEARN WHY DEFINING THESE VARIABLES IS IMPORTANT: https://disqus.com/admin/universalcode/#configuration-variables*/
/*
var disqus_config = function () {
this.page.url = PAGE_URL; // Replace PAGE_URL with your page's canonical URL variable
this.page.identifier = PAGE_IDENTIFIER; // Replace PAGE_IDENTIFIER with your page's unique identifier variable
};
*/
(function() { // DON'T EDIT BELOW THIS LINE
var d = document, s = d.createElement('script');
s.src = 'https://help-study.disqus.com/embed.js';
s.setAttribute('data-timestamp', +new Date());
(d.head || d.body).appendChild(s);
})();
Please enable JavaScript to view the comments powered by Disqus.

Copyright 2019. All rights reserved | Read Questions and Answers 2019 Online