Hello, I have been going to the meets for Number sense but it seems I can never get the estimation problems right. I am told there is a trick but don't know what it is. Some one, please help!
This is not an estimation question, but is there a trick to multiplying numbers like this. I only know squares upto 20 thru memorization. 1.) 54*54 Answer : 2916
Hello, I have been going to the meets for Number sense but it seems I can never get the estimation problems right. I am told there is a trick but don't know what it is. Some one, please help!
This is not an estimation question, but is there a trick to multiplying numbers like this. I only know squares upto 20 thru memorization. 1.) 54*54 Answer : 2916
There are several ways to work these typically. Here are my suggestions at first glance: 1.) 931143/ 308
I use quick division, dividing the first 3 digits of the first number by 308: 931 / 308 = 3 with remainder 7 then add the next digit and see if it divides into 308 71 / 308 = 0 with remainder 71 then add the next digit 714/308 = 2 with remainder (who cares after this - you should be within 5%) Finally, you must see that you will have an answer of 4 digits. Answer then is 3020
Alternate = note that 31^2 = 961 so answer is a little less than 3100
2.) 299 * 298 300 * 300 = 90000
3.) 71% of 5192 71% * 5200 is approximately 3500 + 140 = 3640
4.) 392*187 I would approximate by (392+8) * (187 - 8), or 400 * 180 = 72000
5.) 508*309 I would approximate by (508 - 8) * (309 + 8), or 500 * 317 = 158500
6.) 148 divided by 6 3/7 I would use 148 * 7/45 = 1000 / 45 which is just over 22
7.) 21+37+42+18+53+89 For this style you can usually round each number to the nearest 10 and add: 20 + 40 + 40 + 20 + 50 + 90 = 100 + 70 + 90 = 260 Answer: 247-273
8.) 1792 divided by 13.2 Note 13^2 = 169, so 179 / 13 is a little more than 13. Also you will have one more digit so write down a little more than 130... say 134 (although 130 would also work in this case...takes practice to know when to decide how precise you need to be)
