GRADE FIVE MATH­E­MAT­ICS

Stabroek News Sunday - - WEEKEND MAGAZINE -

Hello Boys and Girls! Did you have an ex­cit­ing week? I hope you chal­lenged your­self to com­plete all your tasks. This week, our top­ics will be Mul­ti­ples and Low­est Com­mon Mul­ti­ple. We will also add and sub­tract Frac­tions.

First, let us look at the an­swers for last week’s items.

An­swers for last week Prime or Com­pos­ite 1.12 –C, 2. 13 – P, 6. 24-C, 7. 25 – C , 11. 41- P, 12. 43 – P, 16. 60 –C, 17. 63 –C,

Prime Fac­tors 1. 8= 2 x 2x 2 2. 10= 2 x 5 3. 15= 3 x 5 4. 16= 2 x 2 x 2 x 2 5. 20=2 x 2 x 5 6. 24=2 x 2 x 2 x 3 7. 28=2 x 2 x 7 8. 60= 2 x 2 x 3 x5 9. 72= 2 x 2 x 2 x 3 x 3 10.96=2 x 2 x 2 x 2 x 2 x 3

Com­mon Fac­tors 1. 6 and 9=3 2. 6 and 8=2 3. 12 and 16= 2 and 4 4. 9 and 12 = 3 5. 8 and 20 = 2and 4 6. 18 and 30= 3and 6 7. 25 and 40 =5 8. 15 and 20=5 9. 24 and 42=2,3,6 10.36 and 48=2,3,4,6,12

Let’s now move on to this week’s work.

Mul­ti­ples When you learned your times ta­bles in grammar school, you were learn­ing mul­ti­ples. For ex­am­ple, 2, 4, 6, 8, and 10 are mul­ti­ples of 2. To get these num­bers, you mul­ti­plied 2 by 1, 2, 3, 4, and 5, which are whole num­bers. A mul­ti­ple of a num­ber is that num­ber mul­ti­plied by a whole num­ber.

Prac­tice Ac­tiv­ity Write down the first 5 mul­ti­ples of the fol­low­ing 1.2 2. 3 3. 4 4. 5 5. 6 6. 7

Low­est Com­mon Mul­ti­ple The low­est com­mon mul­ti­ple of a group of num­bers is their com­mon mul­ti­ple with the low­est or small­est value. We can find the low­est com­mon mul­ti­ple by ei­ther list­ing them or do­ing re­peated di­vi­sion by prime num­bers. We did re­peated di­vi­sion by prime num­bers when we found the square root of num­bers. Re­mem­ber: When do­ing re­peated di­vi­sion:

- If the num­ber does not di­vide ex­actly, we bring it down - We di­vide un­til we get 1.

e.g. What is the Low­est Com­mon Mul­ti­ple of 2 and 3? 2 2, 3 Please in­sert ver­ti­cal line to show re­peated di­vi­sion. 3 1, 3 1, 1 LCM= 2x3= 6

Prac­tice Ex­er­cise Use any method that you are com­fort­able with, to find the L.C.M of the fol­low­ing num­bers. 1. 2,3 2. 2,4 3. 3,4 4. 3,7 5. 3,18 6. 2,3,6 7. 6,8,12 8. 3,4,8 9. 4,6,9 10.4,5,10

Solve the fol­low­ing prob­lems. 1. Write down any com­mon mul­ti­ple of the de­nom­i­na­tors of the fol­low ing frac­tions.

2. What is the least num­ber of boys that can be placed in rows of 6,8 or 12 with­out any be­ing left out? 3. To­day, both the soc­cer team and the bas­ket­ball team had games. The soc­cer team plays ev­ery 3 days and the bas­ket­ball team plays ev­ery 5 days. When will both teams have games on the same day again? 4. A man­ager at a restau­rant can buy ham­burger buns in pack­ages of 8 and ham­burger pat­ties in pack­ages of 6. Sup­pose the man­ager can­not buy part of a pack­ages. What is the least num­ber of pack­ages of each prod­uct he can buy to have an equal num­ber of ham­burger pat­ties and buns? 5. A man smiles at his wife ev­ery 3 sec­onds while the wife smiles back ev­ery 6 sec­onds. When will both hus­band and wife smile at each other at the same time? 6. Steve can save 9 dol­lars ev­ery day while Maria can save 12 dol­lars. What is the least num­ber of days it will take each per­son to save the same amount of money? 7. Boxes that are 12 cen­time­tres tall are be­ing piled next to boxes that are 10 cen­time­tres tall. What is the least height at which the two piles will be the same height? 8. A ra­dio sta­tion plays “yes­ter­day” by the Bea­tles once ev­ery 2 days. An­other sta­tion plays the same song once ev­ery 3 days. How many times in 30 days will both ra­dio sta­tions play the same song on the same day? 9. Two men run­ning a marathon took a sip of wa­ter at the same time 72 min­utes af­ter they started the race. If the first man took a sip of wa­ter ev­ery 9 min­utes, how of­ten did the other man take a sip of wa­ter? 10. A train to New York city leaves a sta­tion ev­ery 7 min­utes. An­other train to Bos­ton leaves the sta­tion ev­ery 6 min­utes. Sup­pose it is 6:30 am right now. At what time will both trains leave the sta­tion to­gether?

Re­mem­ber : Al­ways ask your­self the fol­low­ing ques­tions when you want to solve a word prob­lem: - What is the sum telling me? - What is the sum ask­ing me?

Can you re­mem­ber how to add and sub­tract frac­tions? Use the skills that you have mas­tered, to work the fol­low­ing frac­tion sums. You will be sup­plied with all the an­swers for this week’s work, next week.

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