Tse ka Hare
Litlhaloso tsa mantlha
Rectangle ke quadrilateral moo likhutlo tsohle li lekanang. Li boetse li otlolohile 'me li 90 °.
Pherimitha ke kakaretso ea bolelele ba mahlakore ohle a poligone. Lebitso le amoheloang ka kakaretso ke lengolo le leholo la Selatine P. Tlas'a "P", ho bonolo ho ngola lebitso la setšoantšo ka litlhaku tse nyenyane e le hore u se ke ua ferekanngoa mesebetsing ea tseleng.
Haeba bolelele ba mahlakoreng bo fanoe ka lihlopha tse fapaneng, re ke ke ra khona ho fumana hore na moeli oa khutlontsi ke ofe. Ka hona, bakeng sa tharollo e nepahetseng, hoa hlokahala ho fetolela data eohle ho tekanyo e le 'ngoe ea tekanyo.
Perimitha e lekantsoeng ka eng?
- millimeter (limilimithara);
- centimeter (cm);
- decimeter (dm);
- metara (m);
- kilometer (km) le diyuniti tse ding tsa bolelele.
Khatisong ena, re tla hlahloba mokhoa oa ho bala perimeter ea khutlonnetsepa le ho sekaseka mehlala ea ho rarolla mathata.
Foromo ea potoloho
Pherimitha (P) ea khutlonnetsepa e lekana le kakaretso ea bolelele ba mahlakore ohle a eona.
P = a + b + a + b
Hobane mahlakore a fapaneng a setšoantšo sena a lekana, foromo e ka emeloa ka tsela e latelang:
- Mahlakore a mabeli: P = 2*(a+b)
- Kakaretso ea litekanyetso tse habeli tsa mahlakore: P = 2a+2b
Lehlakore le lekgutshwanyane ke bophahamo/bophara ba khutlonnetsepa, lehlakore le lelelele ke motheo/bolelele ba lona.
Mehlala ea mesebetsi
Mosebetsi 1
Fumana pherimitha ea khutlonnetsepa haeba mahlakore a eona a le 5 cm le 8 cm.
Qeto:
Re kenya boleng bo tsebahalang u2bu5binto foromo ebe re fumana: P u8d 26 * (XNUMX cm + XNUMX cm) uXNUMXd XNUMX cm.
Mosebetsi 2
Sebaka sa khutlonnetsepa ke 20 cm, 'me e' ngoe ea mahlakore a eona ke 4 cm. Fumana lehlakore la bobeli la setšoantšo.
Qeto:
Joalokaha re tseba, P=2a+2b. Ha re re 4 cm ke lehlakore а. Kahoo lehlakore le sa tsejoeng b, e atolositsoeng ka tse peli, e baloa ka tsela e latelang: 2b u2d P - 20a u2d 4 cm - 12 * XNUMX cm uXNUMXd XNUMX cm.
Ka hona, lehlakore b = 12 cm / 2 = 6 cm.
Bothata ba ho rarolla
'Me joale itloaetse!
1. Lehlakore le leng la khutlonnetsepa ke 9cm mme le leng le bolelele ba 11cm. Mokhoa oa ho tseba perimeter?
Re etsa qeto joang:
Haeba a = 9, joale b = 9 + 11;
Joale b = 20 cm;
Ha re sebeliseng foromo P = 2 × (a + b);
P = 2 × (9 + 20);
Karabo: 58 cm.
2. Fumana pherimitha ea khutlontsi e nang le mahlakore a 30 mm le 4 cm. Hlalosa karabo ea hau ka lisentimitara.
Re etsa qeto joang:
Fetolela 30 mm ho cm:
30 limilimithara = 3 cm,.
Sebelisa foromo bakeng sa pherimithara ea khutlonnetsepa:
P \u003d 3 + 4 + 3 + 4 \u003d 14 cm.
Karabo: P = 14 cm.
3. Fumana pherimitha ea triangolo e nang le mahlakore a 2 ho le 300 mm. Hlalosa karabo ea hau ka lisentimitara.
Re etsa qeto joang:
Ha re fetole bolelele ba mahlakore ho lisentimitara:
2 dm = 20 cm, 300 mm = 30 cm.
Fumana pherimitha ho sebelisa foromo P = 2 × (a + b):
P \u003d 2 × (20 + 30) \u003d 2 × 50 \u003d 100 (cm).
Karabo: P = 100 cm.
